nSum
LC 1. Two Sum 两数之和
https://leetcode.com/problems/two-sum/
LC 15. 3Sum 三数之和
https://leetcode.com/problems/3sum/
LC 167. Two Sum II - Input Array Is Sorted 两数之和 II- 输入有序数组
https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/
LC 18. 4Sum 四数之和
https://leetcode.com/problems/4sum/
双指针数组
LC 75. Sort Colors 颜色分类
https://leetcode.com/problems/sort-colors/
& More