DFS——选数问题

#include<stdio.h>
#include<vector> 
using namespace std;
const int maxn = 30;
int n, k, x, maxSumSqu = -1, A[maxn];
vector<int> temp;
vector<int> ans;

void DFS(int index, int nowK, int sum, int sumSqu)
{
    
    
	if(nowK == k && sum == x)
	{
    
    
		if(sumSqu > maxSumSqu)
		{
    
    
			maxSumSqu = sumSqu;
			ans = temp;
		}
		return;
	}
	if(index > n || nowK > k || sum > x) return; 
	
	// 岔路口 —— 选
	temp.push_back(A[index]);
	DFS(index + 1, nowK + 1, sum + A[index], sumSqu + A[index] * A[index]);
	temp.pop_back();
	
	// 岔路口 —— 不选
	DFS(index + 1, nowK, sum, sumSqu);   
	
}

int main()
{
    
    
    // ......
	return 0;
}