Skip to main content

LeetCode Solutions - Page 4

367. Valid Perfect Square​

Junior

Description:

Given a positive integer num, return true if num is a perfect square or false otherwise.

A perfect square is an integer that is the square of an integer. In other words, it is the product of some integer with itself.

You must not use any built-in library function, such as sqrt.

Example 1:

Input: num = 16
Output: true
Explanation: We return true because 4 * 4 = 16 and 4 is an integer.

Example 2:

Input: num = 14
Output: false
Explanation: We return false because 3.742 * 3.742 = 14 and 3.742 is not an integer.

Constraints:

  • 1 <= num <= 2^31 - 1

Code:

// PHP solution for this challenge is currently being updated.

389. Find the Difference​

Junior

Description:

You are given two strings s and t.

String t is generated by random shuffling string s and then add one more letter at a random position.

Return the letter that was added to t.

Example 1:

Input: s = "abcd", t = "abcde"
Output: "e"
Explanation: 'e' is the letter that was added.

Example 2:

Input: s = "", t = "y"
Output: "y"

Constraints:

  • 0 <= s.length <= 1000
  • t.length == s.length + 1
  • s and t consist of lowercase English letters.

Code:

// PHP solution for this challenge is currently being updated.

401. Binary Watch​

Junior

Description:

A binary watch has 4 LEDs on the top to represent the hours (0-11), and 6 LEDs on the bottom to represent the minutes (0-59). Each LED represents a zero or one, with the least significant bit on the right.

  • For example, the below binary watch reads "4:51".

Given an integer turnedOn which represents the number of LEDs that are currently on (ignoring the PM), return all possible times the watch could represent. You may return the answer in any order.

The hour must not contain a leading zero.

  • For example, "01:00" is not valid. It should be "1:00".

The minute must consist of two digits and may contain a leading zero.

  • For example, "10:2" is not valid. It should be "10:02".

Example 1:

Input: turnedOn = 1
Output: ["0:01","0:02","0:04","0:08","0:16","0:32","1:00","2:00","4:00","8:00"]

Example 2:

Input: turnedOn = 9
Output: []

Constraints:

  • 0 <= turnedOn <= 10

Code:

// PHP solution for this challenge is currently being updated.

404. Sum of Left Leaves​

Junior

Description:

Given the root of a binary tree, return the sum of all left leaves.

A leaf is a node with no children. A left leaf is a leaf that is the left child of another node.

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: 24
Explanation: There are two left leaves in the binary tree, with values 9 and 15 respectively.

Example 2:

Input: root = [1]
Output: 0

Constraints:

  • The number of nodes in the tree is in the range [1, 1000].
  • -1000 <= Node.val <= 1000

Code:

// PHP solution for this challenge is currently being updated.

409. Longest Palindrome​

Junior

Description:

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

Letters are case sensitive, for example, "Aa" is not considered a palindrome.

Example 1:

Input: s = "abccccdd"
Output: 7
Explanation: One longest palindrome that can be built is "dccaccd", whose length is 7.

Example 2:

Input: s = "a"
Output: 1
Explanation: The longest palindrome that can be built is "a", whose length is 1.

Constraints:

  • 1 <= s.length <= 2000
  • s consists of lowercase and/or uppercase English letters only.

Code:

// PHP solution for this challenge is currently being updated.

512. Game Play Analysis II 🔒​

Junior

Description:

Table: Activity

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| player_id    | int     |
| device_id    | int     |
| event_date   | date    |
| games_played | int     |
+--------------+---------+
(player_id, event_date) is the primary key (combination of columns with unique values) of this table.
This table shows the activity of players of some games.
Each row is a record of a player who logged in and played a number of games (possibly 0) before logging out on someday using some device.

Write a solution to report the device that is first logged in for each player.

Return the result table in any order.

The result format is in the following example.

Example 1:

Input:
Activity table:
+-----------+-----------+------------+--------------+
| player_id | device_id | event_date | games_played |
+-----------+-----------+------------+--------------+
| 1         | 2         | 2017-03-01 | 5            |
| 1         | 2         | 2017-05-02 | 6            |
| 2         | 3         | 2018-06-25 | 1            |
| 3         | 1         | 2017-03-02 | 0            |
| 3         | 4         | 2019-07-03 | 5            |
+-----------+-----------+------------+--------------+
Output:
+-----------+-----------+
| player_id | device_id |
+-----------+-----------+
| 1         | 2         |
| 2         | 3         |
| 3         | 1         |
+-----------+-----------+

Code:

// PHP solution for this challenge is currently being updated.

589. N-ary Tree Preorder Traversal​

Junior

Description:

Given the root of an n-ary tree, return the preorder traversal of its nodes' values.

Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples)

Example 1:

Input: root = [1,null,3,2,4,null,5,6]
Output: [1,3,5,6,2,4]

Example 2:

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
Output: [1,2,3,6,7,11,14,4,8,12,5,9,13,10]

Constraints:

  • The number of nodes in the tree is in the range [0, 10^4].
  • 0 <= Node.val <= 10^4
  • The height of the n-ary tree is less than or equal to 1000.

Follow up: Recursive solution is trivial, could you do it iteratively?

Code:

// PHP solution for this challenge is currently being updated.

590. N-ary Tree Postorder Traversal​

Junior

Description:

Given the root of an n-ary tree, return the postorder traversal of its nodes' values.

Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples)

Example 1:

Input: root = [1,null,3,2,4,null,5,6]
Output: [5,6,3,2,4,1]

Example 2:

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
Output: [2,6,14,11,7,3,12,8,4,13,9,10,5,1]

Constraints:

  • The number of nodes in the tree is in the range [0, 10^4].
  • 0 <= Node.val <= 10^4
  • The height of the n-ary tree is less than or equal to 1000.

Follow up: Recursive solution is trivial, could you do it iteratively?

Code:

// PHP solution for this challenge is currently being updated.

603. Consecutive Available Seats 🔒​

Junior

Description:

Table: Cinema

+-------------+------+
| Column Name | Type |
+-------------+------+
| seat_id     | int  |
| free        | bool |
+-------------+------+
seat_id is an auto-increment column for this table.
Each row of this table indicates whether the i^th seat is free or not. 1 means free while 0 means occupied.

Find all the consecutive available seats in the cinema.

Return the result table ordered by seat_id in ascending order.

The test cases are generated so that more than two seats are consecutively available.

The result format is in the following example.

Example 1:

Input:
Cinema table:
+---------+------+
| seat_id | free |
+---------+------+
| 1       | 1    |
| 2       | 0    |
| 3       | 1    |
| 4       | 1    |
| 5       | 1    |
+---------+------+
Output:
+---------+
| seat_id |
+---------+
| 3       |
| 4       |
| 5       |
+---------+

Code:

// PHP solution for this challenge is currently being updated.

613. Shortest Distance in a Line 🔒​

Junior

Description:

Table: Point

+-------------+------+
| Column Name | Type |
+-------------+------+
| x           | int  |
+-------------+------+
In SQL, x is the primary key column for this table.
Each row of this table indicates the position of a point on the X-axis.

Find the shortest distance between any two points from the Point table.

The result format is in the following example.

Example 1:

Input:
Point table:
+----+
| x  |
+----+
| -1 |
| 0  |
| 2  |
+----+
Output:
+----------+
| shortest |
+----------+
| 1        |
+----------+
Explanation: The shortest distance is between points -1 and 0 which is |(-1) - 0| = 1.

Follow up: How could you optimize your solution if the Point table is ordered in ascending order?

Code:

// PHP solution for this challenge is currently being updated.

628. Maximum Product of Three Numbers​

Junior

Description:

Given an integer array nums, find three numbers whose product is maximum and return the maximum product.

Example 1:

Input: nums = [1,2,3]
Output: 6

Example 2:

Input: nums = [1,2,3,4]
Output: 24

Example 3:

Input: nums = [-1,-2,-3]
Output: -6

Constraints:

  • 3 <= nums.length <= 10^4
  • -1000 <= nums[i] <= 1000

Code:

// PHP solution for this challenge is currently being updated.

637. Average of Levels in Binary Tree​

Junior

Description: Given the root of a binary tree, return the average value of the nodes on each level in the form of an array. Answers within 10^-5 of the actual answer will be accepted.

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: [3.00000,14.50000,11.00000]
Explanation: The average value of nodes on level 0 is 3, on level 1 is 14.5, and on level 2 is 11.
Hence return [3, 14.5, 11].

Example 2:

Input: root = [3,9,20,15,7]
Output: [3.00000,14.50000,11.00000]

Constraints:

  • The number of nodes in the tree is in the range [1, 10^4].
  • -2^31 <= Node.val <= 2^31 - 1

Code:

// PHP solution for this challenge is currently being updated.

645. Set Mismatch​

Junior

Description:

You have a set of integers s, which originally contains all the numbers from 1 to n. Unfortunately, due to some error, one of the numbers in s got duplicated to another number in the set, which results in repetition of one number and loss of another number.

You are given an integer array nums representing the data status of this set after the error.

Find the number that occurs twice and the number that is missing and return them in the form of an array.

Example 1:

Input: nums = [1,2,2,4]
Output: [2,3]

Example 2:

Input: nums = [1,1]
Output: [1,2]

Constraints:

  • 2 <= nums.length <= 10^4
  • 1 <= nums[i] <= 10^4

Code:

// PHP solution for this challenge is currently being updated.

693. Binary Number with Alternating Bits​

Junior

Description:

Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values.

Example 1:

Input: n = 5
Output: true
Explanation: The binary representation of 5 is: 101

Example 2:

Input: n = 7
Output: false
Explanation: The binary representation of 7 is: 111.

Example 3:

Input: n = 11
Output: false
Explanation: The binary representation of 11 is: 1011.

Constraints:

  • 1 <= n <= 2^31 - 1

Code:

// PHP solution for this challenge is currently being updated.

705. Design HashSet​

Junior

Description:

Design a HashSet without using any built-in hash table libraries.

Implement MyHashSet class:

  • void add(key) Inserts the value key into the HashSet.
  • bool contains(key) Returns whether the value key exists in the HashSet or not.
  • void remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.

Example 1:

Input
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]

Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // return False, (already removed)

Constraints:

  • 0 <= key <= 10^6
  • At most 10^4 calls will be made to add, remove, and contains.

Code:

// PHP solution for this challenge is currently being updated.

733. Flood Fill​

Junior

Description:

You are given an image represented by an m x n grid of integers image, where image[i][j] represents the pixel value of the image. You are also given three integers sr, sc, and color. Your task is to perform a flood fill on the image starting from the pixel image[sr][sc].

To perform a flood fill:

  • Begin with the starting pixel and change its color to color.
  • Perform the same process for each pixel that is directly adjacent (pixels that share a side with the original pixel, either horizontally or vertically) and shares the same color as the starting pixel.
  • Keep repeating this process by checking neighboring pixels of the updated pixels and modifying their color if it matches the original color of the starting pixel.
  • The process stops when there are no more adjacent pixels of the original color to update.

Return the modified image after performing the flood fill.

Example 1:

Input: image = [[1,1,1],[1,1,0],[1,0,1]], sr = 1, sc = 1, color = 2

Output: [[2,2,2],[2,2,0],[2,0,1]]

Explanation:

From the center of the image with position (sr, sc) = (1, 1) (i.e., the red pixel), all pixels connected by a path of the same color as the starting pixel (i.e., the blue pixels) are colored with the new color.

Note the bottom corner is not colored 2, because it is not horizontally or vertically connected to the starting pixel.

Example 2:

Input: image = [[0,0,0],[0,0,0]], sr = 0, sc = 0, color = 0

Output: [[0,0,0],[0,0,0]]

Explanation:

The starting pixel is already colored with 0, which is the same as the target color. Therefore, no changes are made to the image.

Constraints:

  • m == image.length
  • n == image[i].length
  • 1 <= m, n <= 50
  • 0 &lt;= image[i][j], color < 2^16
  • 0 &lt;= sr < m
  • 0 &lt;= sc < n

Code:

// PHP solution for this challenge is currently being updated.

746. Min Cost Climbing Stairs​

Junior

Description:

You are given an integer array cost where cost[i] is the cost of i^th step on a staircase. Once you pay the cost, you can either climb one or two steps.

You can either start from the step with index 0, or the step with index 1.

Return the minimum cost to reach the top of the floor.

Example 1:

Input: cost = [10,_15_,20]
Output: 15
Explanation: You will start at index 1.
- Pay 15 and climb two steps to reach the top.
The total cost is 15.

Example 2:

Input: cost = [_1_,100,_1_,1,_1_,100,_1_,_1_,100,_1_]
Output: 6
Explanation: You will start at index 0.
- Pay 1 and climb two steps to reach index 2.
- Pay 1 and climb two steps to reach index 4.
- Pay 1 and climb two steps to reach index 6.
- Pay 1 and climb one step to reach index 7.
- Pay 1 and climb two steps to reach index 9.
- Pay 1 and climb one step to reach the top.
The total cost is 6.

Constraints:

  • 2 &lt;= cost.length &lt;= 1000
  • 0 &lt;= cost[i] &lt;= 999

Code:

// PHP solution for this challenge is currently being updated.

961. N-Repeated Element in Size 2N Array​

Junior

Description:

You are given an integer array nums with the following properties:

  • nums.length == 2 * n.
  • nums contains n + 1 unique values, n of which occur exactly once in the array.
  • Exactly one element of nums is repeated n times.

Return the element that is repeated n times.

Example 1:

Input: nums = [1,2,3,3]
Output: 3

Example 2:

Input: nums = [2,1,2,5,3,2]
Output: 2

Example 3:

Input: nums = [5,1,5,2,5,3,5,4]
Output: 5

Constraints:

  • 2 &lt;= n &lt;= 5000
  • nums.length == 2 * n
  • 0 &lt;= nums[i] &lt;= 10^4
  • nums contains n + 1 unique elements and one of them is repeated exactly n times.

Code:

// PHP solution for this challenge is currently being updated.

1051. Height Checker​

Junior

Description:

A school is trying to take an annual photo of all the students. The students are asked to stand in a single file line in non-decreasing order by height. Let this ordering be represented by the integer array expected where expected[i] is the expected height of the i^th student in line.

You are given an integer array heights representing the current order that the students are standing in. Each heights[i] is the height of the i^th student in line (0-indexed).

Return _the number of indices where _heights[i] != expected[i].

Example 1:

Input: heights = [1,1,4,2,1,3]
Output: 3
Explanation:
heights:  [1,1,_4_,2,_1_,_3_]
expected: [1,1,_1_,2,_3_,_4_]
Indices 2, 4, and 5 do not match.

Example 2:

Input: heights = [5,1,2,3,4]
Output: 5
Explanation:
heights:  [_5_,_1_,_2_,_3_,_4_]
expected: [_1_,_2_,_3_,_4_,_5_]
All indices do not match.

Example 3:

Input: heights = [1,2,3,4,5]
Output: 0
Explanation:
heights:  [1,2,3,4,5]
expected: [1,2,3,4,5]
All indices match.

Constraints:

  • 1 &lt;= heights.length &lt;= 100
  • 1 &lt;= heights[i] &lt;= 100

Code:

// PHP solution for this challenge is currently being updated.

1099. Two Sum Less Than K 🔒​

Junior

Description:

Given an array nums of integers and integer k, return the maximum sum such that there exists i < j with nums[i] + nums[j] = sum and sum < k. If no i, j exist satisfying this equation, return -1.

Example 1:

Input: nums = [34,23,1,24,75,33,54,8], k = 60
Output: 58
Explanation: We can use 34 and 24 to sum 58 which is less than 60.

Example 2:

Input: nums = [10,20,30], k = 15
Output: -1
Explanation: In this case it is not possible to get a pair sum less that 15.

Constraints:

  • 1 &lt;= nums.length &lt;= 100
  • 1 &lt;= nums[i] &lt;= 1000
  • 1 &lt;= k &lt;= 2000

Code:

// PHP solution for this challenge is currently being updated.

1150. Check If a Number Is Majority Element in a Sorted Array 🔒​

Junior

Description:

Given an integer array nums sorted in non-decreasing order and an integer target, return true if target is a majority element, or false otherwise.

A majority element in an array nums is an element that appears more than nums.length / 2 times in the array.

Example 1:

Input: nums = [2,4,5,5,5,5,5,6,6], target = 5
Output: true
Explanation: The value 5 appears 5 times and the length of the array is 9.
Thus, 5 is a majority element because 5 > 9/2 is true.

Example 2:

Input: nums = [10,100,101,101], target = 101
Output: false
Explanation: The value 101 appears 2 times and the length of the array is 4.
Thus, 101 is not a majority element because 2 > 4/2 is false.

Constraints:

  • 1 &lt;= nums.length &lt;= 1000
  • 1 &lt;= nums[i], target &lt;= 10^9
  • nums is sorted in non-decreasing order.

Code:

// PHP solution for this challenge is currently being updated.

1176. Diet Plan Performance 🔒​

Junior

Description:

A dieter consumes calories[i] calories on the i-th day.

Given an integer k, for every consecutive sequence of k days (calories[i], calories[i+1], ..., calories[i+k-1] for all 0 &lt;= i &lt;= n-k), they look at T, the total calories consumed during that sequence of k days (calories[i] + calories[i+1] + ... + calories[i+k-1]):

  • If T < lower, they performed poorly on their diet and lose 1 point;
  • If T > upper, they performed well on their diet and gain 1 point;
  • Otherwise, they performed normally and there is no change in points.

Initially, the dieter has zero points. Return the total number of points the dieter has after dieting for calories.length days.

Note that the total points can be negative.

Example 1:

Input: calories = [1,2,3,4,5], k = 1, lower = 3, upper = 3
Output: 0
Explanation: Since k = 1, we consider each element of the array separately and compare it to lower and upper.
calories[0] and calories[1] are less than lower so 2 points are lost.
calories[3] and calories[4] are greater than upper so 2 points are gained.

Example 2:

Input: calories = [3,2], k = 2, lower = 0, upper = 1
Output: 1
Explanation: Since k = 2, we consider subarrays of length 2.
calories[0] + calories[1] > upper so 1 point is gained.

Example 3:

Input: calories = [6,5,0,0], k = 2, lower = 1, upper = 5
Output: 0
Explanation:
calories[0] + calories[1] > upper so 1 point is gained.
lower <= calories[1] + calories[2] <= upper so no change in points.
calories[2] + calories[3] < lower so 1 point is lost.

Constraints:

  • 1 &lt;= k &lt;= calories.length &lt;= 10^5
  • 0 &lt;= calories[i] &lt;= 20000
  • 0 &lt;= lower &lt;= upper

Code:

// PHP solution for this challenge is currently being updated.

1228. Missing Number In Arithmetic Progression 🔒​

Junior

Description:

In some array arr, the values were in arithmetic progression: the values arr[i + 1] - arr[i] are all equal for every 0 &lt;= i < arr.length - 1.

A value from arr was removed that was not the first or last value in the array.

Given arr, return the removed value.

Example 1:

Input: arr = [5,7,11,13]
Output: 9
Explanation: The previous array was [5,7,9,11,13].

Example 2:

Input: arr = [15,13,12]
Output: 14
Explanation: The previous array was [15,14,13,12].

Constraints:

  • 3 &lt;= arr.length &lt;= 1000
  • 0 &lt;= arr[i] &lt;= 10^5
  • The given array is guaranteed to be a valid array.

Code:

// PHP solution for this challenge is currently being updated.

1252. Cells with Odd Values in a Matrix​

Junior

Description:

There is an m x n matrix that is initialized to all 0's. There is also a 2D array indices where each indices[i] = [r~i, c~i] represents a 0-indexed location to perform some increment operations on the matrix.

For each location indices[i], do both of the following:

  • Increment all the cells on row r~i.
  • Increment all the cells on column c~i.

Given m, n, and indices, return _the number of odd-valued cells in the matrix after applying the increment to all locations in _indices.

Example 1:

Input: m = 2, n = 3, indices = [[0,1],[1,1]]
Output: 6
Explanation: Initial matrix = [[0,0,0],[0,0,0]].
After applying first increment it becomes [[1,2,1],[0,1,0]].
The final matrix is [[1,3,1],[1,3,1]], which contains 6 odd numbers.

Example 2:

Input: m = 2, n = 2, indices = [[1,1],[0,0]]
Output: 0
Explanation: Final matrix = [[2,2],[2,2]]. There are no odd numbers in the final matrix.

Constraints:

  • 1 &lt;= m, n &lt;= 50
  • 1 &lt;= indices.length &lt;= 100
  • 0 &lt;= r~i < m
  • 0 &lt;= c~i < n

Follow up: Could you solve this in O(n + m + indices.length) time with only O(n + m) extra space?

Code:

// PHP solution for this challenge is currently being updated.

1304. Find N Unique Integers Sum up to Zero​

Junior

Description:

Given an integer n, return any array containing n unique integers such that they add up to 0.

Example 1:

Input: n = 5
Output: [-7,-1,1,3,4]
Explanation: These arrays also are accepted [-5,-1,1,2,3] , [-3,-1,2,-2,4].

Example 2:

Input: n = 3
Output: [-1,0,1]

Example 3:

Input: n = 1
Output: [0]

Constraints:

  • 1 &lt;= n &lt;= 1000

Code:

// PHP solution for this challenge is currently being updated.

1317. Convert Integer to the Sum of Two No-Zero Integers​

Junior

Description:

No-Zero integer is a positive integer that does not contain any 0 in its decimal representation.

Given an integer n, return a list of two integers [a, b] where:

  • a and b are No-Zero integers.
  • a + b = n

The test cases are generated so that there is at least one valid solution. If there are many valid solutions, you can return any of them.

Example 1:

Input: n = 2
Output: [1,1]
Explanation: Let a = 1 and b = 1.
Both a and b are no-zero integers, and a + b = 2 = n.

Example 2:

Input: n = 11
Output: [2,9]
Explanation: Let a = 2 and b = 9.
Both a and b are no-zero integers, and a + b = 11 = n.
Note that there are other valid answers as [8, 3] that can be accepted.

Constraints:

  • 2 &lt;= n &lt;= 10^4

Code:

// PHP solution for this challenge is currently being updated.

1365. How Many Numbers Are Smaller Than the Current Number​

Junior

Description:

Given the array nums, for each nums[i] find out how many numbers in the array are smaller than it. That is, for each nums[i] you have to count the number of valid j&#39;s such that j != i and nums[j] < nums[i].

Return the answer in an array.

Example 1:

Input: nums = [8,1,2,2,3]
Output: [4,0,1,1,3]
Explanation:
For nums[0]=8 there exist four smaller numbers than it (1, 2, 2 and 3).
For nums[1]=1 does not exist any smaller number than it.
For nums[2]=2 there exist one smaller number than it (1).
For nums[3]=2 there exist one smaller number than it (1).
For nums[4]=3 there exist three smaller numbers than it (1, 2 and 2).

Example 2:

Input: nums = [6,5,4,8]
Output: [2,1,0,3]

Example 3:

Input: nums = [7,7,7,7]
Output: [0,0,0,0]

Constraints:

  • 2 &lt;= nums.length &lt;= 500
  • 0 &lt;= nums[i] &lt;= 100

Code:

// PHP solution for this challenge is currently being updated.

1502. Can Make Arithmetic Progression From Sequence​

Junior

Description:

A sequence of numbers is called an arithmetic progression if the difference between any two consecutive elements is the same.

Given an array of numbers arr, return true if the array can be rearranged to form an arithmetic progression. Otherwise, return false.

Example 1:

Input: arr = [3,5,1]
Output: true
Explanation: We can reorder the elements as [1,3,5] or [5,3,1] with differences 2 and -2 respectively, between each consecutive elements.

Example 2:

Input: arr = [1,2,4]
Output: false
Explanation: There is no way to reorder the elements to obtain an arithmetic progression.

Constraints:

  • 2 &lt;= arr.length &lt;= 1000
  • -10^6 &lt;= arr[i] &lt;= 10^6

Code:

// PHP solution for this challenge is currently being updated.

1550. Three Consecutive Odds​

Junior

Description: Given an integer array arr, return true if there are three consecutive odd numbers in the array. Otherwise, return false.

Example 1:

Input: arr = [2,6,4,1]
Output: false
<b>Explanation:</b> There are no three consecutive odds.

Example 2:

Input: arr = [1,2,34,3,4,5,7,23,12]
Output: true
<b>Explanation:</b> [5,7,23] are three consecutive odds.

Constraints:

  • 1 &lt;= arr.length &lt;= 1000
  • 1 &lt;= arr[i] &lt;= 1000

Code:

// PHP solution for this challenge is currently being updated.

1588. Sum of All Odd Length Subarrays​

Junior

Description:

Given an array of positive integers arr, return _the sum of all possible odd-length subarrays of _arr.

A subarray is a contiguous subsequence of the array.

Example 1:

Input: arr = [1,4,2,5,3]
Output: 58
Explanation: The odd-length subarrays of arr and their sums are:
[1] = 1
[4] = 4
[2] = 2
[5] = 5
[3] = 3
[1,4,2] = 7
[4,2,5] = 11
[2,5,3] = 10
[1,4,2,5,3] = 15
If we add all these together we get 1 + 4 + 2 + 5 + 3 + 7 + 11 + 10 + 15 = 58

Example 2:

Input: arr = [1,2]
Output: 3
<b>Explanation: </b>There are only 2 subarrays of odd length, [1] and [2]. Their sum is 3.

Example 3:

Input: arr = [10,11,12]
Output: 66

Constraints:

  • 1 &lt;= arr.length &lt;= 100
  • 1 &lt;= arr[i] &lt;= 1000

Follow up:

Could you solve this problem in O(n) time complexity?

Code:

// PHP solution for this challenge is currently being updated.