题解 | #目标和#

import java.util.*;


public class Solution {
    
    public int res = 0;
    
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param nums int整型一维数组 
     * @param target int整型 
     * @return int整型
     */
    public int findTargetSumWays (int[] nums, int target) {
        // write code here
        
        if (0 == nums.length) {
            return 0;
        }
        
        process(nums, 0, 0, target);
        return res;
    }
    
    public void process(int[] nums, int index, int num, int target) {
        if (index >= nums.length) {
            if (num == target) {
                res++;
            }
            return;
        }
        process(nums, index + 1, num - nums[index], target);
        process(nums, index + 1, num + nums[index], target);
    }
}