Given two sorted integer arrays nums1 and nums2 and an integer k, return the k pairs with the smallest sums. Each pair consists of one element from nums1 and one element from nums2.
Given an n x n matrix where each row and column is sorted in ascending order, find the kth smallest element in the matrix. The matrix is sorted in both rows and columns, but the kth smallest element is the one in the sorted order, not necessarily distinct.
Given a string, sort its characters based on their frequency of occurrence in descending order. If multiple solutions are possible, any valid answer is acceptable. The frequency of each character refers to how many times it appears in the string.
