leetcode-494. 目标和

 

 

class Solution {
public:

    int res = 0;
    int findTargetSumWays(vector<int>& nums, int target) {
        if(nums.size()==0)
            return 0;
        dfs(nums,0,0,target);
        return res;
    }

    void dfs(vector<int>& nums, int index, int sum, int target){
        if(index>nums.size())
            return;
        if(index==nums.size()){
            if(sum == target){
                res++;
                return;
            }else{
                return;
            }
        }
        dfs(nums,index+1, sum + (-1)*nums[index], target);
        dfs(nums,index+1, sum + nums[index], target);
    }
};