Combination Sum (https://leetcode.com/problems/combination-sum/)

Given a set of candidate numbers (candidates) (without duplicates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target.

The same repeated number may be chosen from candidates unlimited number of times.

Note:

All numbers (including target) will be positive integers. The solution set must not contain duplicate combinations. Example 1:

Input: candidates = [2,3,6,7], target = 7, A solution set is: [ [7], [2,2,3] ] Example 2:

Input: candidates = [2,3,5], target = 8, A solution set is: [ [2,2,2,2], [2,3,3], [3,5] ]

Expression Add Operators(https://leetcode.com/problems/expression-add-operators/)

Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -, or * between the digits so they evaluate to the target value.

Example 1:

Input: num = "123", target = 6 Output: ["1+2+3", "123"] Example 2:

Input: num = "232", target = 8 Output: ["23+2", "2+32"] Example 3:

Input: num = "105", target = 5 Output: ["1*0+5","10-5"] Example 4:

Input: num = "00", target = 0 Output: ["0+0", "0-0", "0*0"] Example 5:

Input: num = "3456237490", target = 9191 Output: []