题目链接：

https://www.lanqiao.cn/problems/1447/learning/?subject_code=1&group_code=4&match_num=12&match_flow=1&origin=cup

思想：dfs暴力枚举过一半的分

代码：

#include<bits/stdc++.h>
using namespace std;#define int long longconst int N = 5e6+5;int n,w[N];
bool st[N];
int res;//表示k个砝码，重量是sum
void dfs(int k,int sum){if(k>n){if(sum>0&&!st[sum]){res++;st[sum]=true;}return;}dfs(k+1,sum-w[k]);  //放右边dfs(k+1,sum);  //不选dfs(k+1,sum+w[k]);   //放左边
}signed main(){ios::sync_with_stdio(false);cin.tie(nullptr);cin>>n;for(int i=1;i<=n;i++){cin>>w[i];}dfs(0,0);cout<<res<<"\n";return 0;	}