Backtracking

Combination Sum

Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order.

Unique Paths III

A robot is located at the top-left corner of a m x n grid (marked as ‘Start’ in the diagram below). The robot can either move right or diagonally at any point of time. The robot is trying to reach the top-right corner of the grid (marked as ‘Star’ in the diagram below). How many possible unique paths are there?