1月初的面试，2轮back to back，面试官问了这些leetcode的变体。所有题都是tag题：
变体：https://leetcode.com/problems/kth-missing-positive-number/description/
原题：https://leetcode.com/problems/interval-list-intersections/description/
变体：https://leetcode.com/problems/binary-tree-right-side-view/description/
原题：https://leetcode.com/problems/custom-sort-string/description/
