Swift

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. ...

The problem Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each row must contain the digits 1-9 without repetition. Each column must contain the digits 1-9 without repetition. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition. Note: A Sudoku board (partially filled) could be valid but is not necessarily solvable. Only the filled cells need to be validated according to the mentioned rules. Examples ...

The problem Given two integers a and b, return the sum of the two integers without using the operators + and -. Examples Input: a = 1, b = 2 Output: 3 Input: a = 2, b = 3 Output: 5 Constraints -1000 <= a, b <= 1000 Explanation From the description of the problem, we learn that we need to figure out the way of adding two numbers without using + or - operators. Let’s visualize this problem and find the way we can do it. ...