题目

题目链接：
https://www.nowcoder.com/practice/7a64b6a6cf2e4e88a0a73af0a967a82b

解法

dfs

参考答案C++

class Solution {public:/*** 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vector* @param target int整型* @return int整型*/int combination(vector<int>& nums, int target) {int cnt = 0;int* ans = &cnt;dfs(nums, target, ans);return *ans;}void dfs(vector<int>& nums, int sum, int* ans) {if (sum == 0) {(*ans)++;return;}if (sum < 0)return;for (int i = 0; i < nums.size(); i++) {sum -= nums[i];dfs(nums, sum, ans);sum += nums[i]; //恢复现场，又叫回溯}}
};

参考答案Java

`import java.util.*;

public class Solution {
/**
* 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 combination (int[] nums, int target) {
int[] ans = {0};
dfs(nums, target, ans);

    return ans[0];
}public void dfs(int[] nums, int sum, int[] ans) {if (sum == 0) {ans[0]++;return;}if (sum < 0) return;for (int i = 0; i < nums.length ; i++) {sum -= nums[i];dfs(nums, sum, ans);sum += nums[i]; //恢复现场}
}

}`

参考答案Go

package main/*** 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*/
func combination(nums []int, target int) int {ans := [1]int{0}dfs(nums, target, &ans)return ans[0]
}func dfs(nums []int, sum int, ans *[1]int) {if sum == 0 {ans[0]++return}if sum < 0 {return}for i := 0; i < len(nums); i++ {sum -= nums[i]dfs(nums, sum, ans)sum += nums[i] //恢复现场 又叫回溯}
}

参考答案PHP

<?php/*** 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*/
function combination( $nums ,  $target )
{$ans = 0;dfs($nums,$target,$ans);return $ans;
}function dfs($nums,$sum,&$ans){if($sum ==0){$ans++;return;}if($sum <0)return;for($i=0;$i<count($nums);$i++){$sum-=$nums[$i];dfs($nums,$sum,$ans);$sum+=$nums[$i];//恢复现场，又叫回溯}
}