Swift

The problem Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. Implement the MinStack class: MinStack() initializes the stack object. void push(int val) pushes the element val onto the stack. void pop() removes the element on the top of the stack. int top() gets the top element of the stack. int getMin() retrieves the minimum element in the stack. You must implement a solution with O(1) time complexity for each function. ...

The problem You are given an array of integers nums, and there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. Return the max sliding window. Examples Input: nums = [1,3,-1,-3,5,3,6,7], k = 3 Output: [3,3,5,5,6,7] Explanation: Window position Max --------------- ----- [1 3 -1] -3 5 3 6 7 3 1 [3 -1 -3] 5 3 6 7 3 1 3 [-1 -3 5] 3 6 7 5 1 3 -1 [-3 5 3] 6 7 5 1 3 -1 -3 [5 3 6] 7 6 1 3 -1 -3 5 [3 6 7] 7 Input: nums = [1], k = 1 Output: [1] Constraints 1 <= nums.length <= 10^5 -10^4 <= nums[i] <= 10^4 1 <= k <= nums.length Explanation Before we jump into the solution, let’s look at our example with nums = [1,3,-1,-3,5,3,6,7], k = 3 We can see that at the first position we have max value 3, which we add to our output array. ...

The problem Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise. A permutation is a rearrangement of all the characters of a string. In other words, return true if one of s1’s permutations is a substring of s2. Examples Input: s1 = "ab", s2 = "eidbaooo" Output: true Explanation: s2 contains one permutation of s1 ("ba"). Input: s1 = "ab", s2 = "eidboaoo" Output: false Constraints 1 <= s1.length, s2.length <= 10^4 s1 and s2 consist of lowercase English letters. Explanation Before we jump into the solution, let’s take a look at the example with input s1 = "ab", s2 = "eidbaooo" We are looking for a permutation of s1 in s2 with the size of s1. In the example, we can see that we have a permutation of s1 = "ab" in s2 = "eidbaooo" but in a different order. ...

The problem Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining. Examples Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6 Explanation: The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Input: height = [4,2,0,3,2,5] Output: 9 Constraints n == height.length 1 <= n <= 2 * 10^4 0 <= height[i] <= 10^5 Explanation Let’s look at our example and determine the algorithm of how much water each position could trap. ...

The problem Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length. Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2. The tests are generated such that there is exactly one solution. You may not use the same element twice. ...