You are given a string s and an array of pairs of indices pairs where each pair pairs[i] = [a, b] represents two indices in the string. You can swap the characters at any of these index pairs any number of times. Your task is to return the lexicographically smallest string that can be obtained after performing the swaps.
You are given two strings s and t of the same length, and an integer maxCost. You want to change string s to string t. The cost of changing the ith character of s to the ith character of t is the absolute difference between their ASCII values. Your task is to find the maximum length of a substring of s that can be changed to match the corresponding substring of t, with the total cost not exceeding maxCost.
You are given a string s and an integer k. A k duplicate removal consists of selecting k adjacent and equal letters from the string and removing them, causing the left and the right side of the deleted substring to concatenate together. Repeat this operation until no more such removals are possible. Return the final string after all removals are done.
Given an integer array arr and an integer difference, find the length of the longest subsequence in arr such that the difference between each adjacent element in the subsequence equals the given difference.
In a gold mine grid of size m x n, each cell contains an integer representing the amount of gold in that cell. A cell with 0 means no gold is present. The task is to find the maximum amount of gold that can be collected by following certain movement rules: You can move one step in any of the four directions (left, right, up, down), but you cannot visit the same cell twice, and you cannot move to a cell that contains 0 gold.
On an 8x8 chessboard, there are multiple black queens and one white king. You are given the positions of the black queens and the white king. Your task is to find all the black queens that can directly attack the white king. A queen can attack the king if they share the same row, column, or diagonal.