LeetCode494目标和(dfs)

题目

想不到dp方程怎么写 写一发搜索试试 还好过了

public class LeetCode494 {
    
    
    int res = 0;
    public int findTargetSumWays(int[] nums, int S) {
    
    
        dfs(nums,S,0,0);
        return res;
    }
    private void dfs(int[] nums, int k, int sum, int step){
    
    
        if (step == nums.length) {
    
    
            if (sum == k) res++;
            return;
        }
        dfs(nums,k,sum+nums[step],step+1);
        dfs(nums,k,sum-nums[step],step+1);
    }
}