39. Combination Sum java solutions

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

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

Note:

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

For example, given candidate set [2, 3, 6, 7] and target 7, 
A solution set is: 

[
  [7],
  [2, 2, 3]
]

public class Solution {
    public List<List<Integer>> ans = new ArrayList<List<Integer>>();
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        List<Integer> list = new ArrayList<Integer>();
        combination(list,candidates,target,0,0);
        return ans;
    }
    
    public void combination(List<Integer> list, int[] can, int target, int sum, int s){
        if(sum == target){
            List<Integer> tmp = new ArrayList<Integer>(list);
            ans.add(tmp);
            return;
        }
        if(sum > target) return;
        for(int i = s; i < can.length; i++){
            list.add(can[i]);
            combination(list,can,target,sum+can[i],i);
            list.remove(list.size()-1);
        }
    }
}

都是套路。 N queen 问题掌握了就OK