bzoj 1673: [Usaco2005 Dec]Scales 天平

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神奇的背包dfs

代码：

#include<iostream>#include<cstdio>#include<queue>#include<vector>#include<algorithm>#include<cstring>#define inf 999999999#define ll long longusing namespace std;int n,m;ll a[1010];ll sum[1010];ll ans=0;void dfs(int x,ll w){if(w>m)return;if(sum[x-1]+w<=m){ans=max(ans,sum[x-1]+w);return;}ans=max(ans,w);for(int i=1; i<x; i++){w+=a[i];dfs(i,w);w-=a[i];}}int main(){scanf("%d%d",&n,&m);for(int i=1; i<=n; i++)scanf("%lld",&a[i]),sum[i]=sum[i-1]+a[i];dfs(n+1,0);printf("%lld\n",ans);return 0;}