LeetCode - Boats to Save People

The problem You are given an array people where people[i] is the weight of the ith person, and an infinite number of boats where each boat can carry a maximum weight of limit. Each boat carries at most two people at the same time, provided the sum of the weight of those people is at most limit. Return the minimum number of boats to carry every given person. Example 1: ...

September 3, 2026 · 3 min · Dmytro Chumakov

LeetCode - First Missing Positive

The problem Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums. You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space. Example 1: Input: nums = [1,2,0] Output: 3 Explanation: The numbers in the range [1,2] are all in the array. Example 2: Input: nums = [3,4,-1,1] Output: 2 Explanation: 1 is in the array but 2 is missing. Example 3: ...

August 29, 2026 · 4 min · Dmytro Chumakov

LeetCode - Subarray Sum Equals K

The problem Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals k. A subarray is a contiguous non-empty sequence of elements within an array. Example 1: Input: nums = [1,1,1], k = 2 Output: 2 Example 2: Input: nums = [1,2,3], k = 3 Output: 2 Constraints: 1 <= nums.length <= 2 * 10^4 -1000 <= nums[i] <= 1000 -10^7 <= k <= 10^7 Explanation Even without visualization, you can see that each of the given examples has two subarrays that can sum up to k. ...

August 25, 2026 · 3 min · Dmytro Chumakov

LeetCode - Longest Common Prefix

The problem Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string "". Example 1: Input: strs = ["flower","flow","flight"] Output: "fl" Example 2: Input: strs = ["dog","racecar","car"] Output: "" Explanation: There is no common prefix among the input strings. Constraints: 1 <= strs.length <= 200 0 <= strs[i].length <= 200 strs[i] consists of only lowercase English letters if it is non-empty. Explanation I’m trying to add a little bit of life to my posts, so I decided to lay down some thought process behind the solution. Please go easy on me. ...

August 22, 2026 · 3 min · Dmytro Chumakov

LeetCode - Sort an Array

The problem Given an array of integers nums, sort the array in ascending order and return it. You must solve the problem without using any built-in functions in O(nlog(n)) time complexity and with the smallest space complexity possible. Example 1: Input: nums = [5,2,3,1] Output: [1,2,3,5] Explanation: After sorting the array, the positions of some numbers are not changed (for example, 2 and 3), while the positions of other numbers are changed (for example, 1 and 5). Example 2: ...

August 17, 2026 · 4 min · Dmytro Chumakov