ural 1005 dp dfs or 0 1背包

就是说不到20堆石头。分成2大堆。。让他们绝对值最小。。

#include<iostream>#include<cstdio>#include<algorithm>using namespace std;int w[22],n,sum[22],ans,ave;void dfs(int idx,int num){    if(num>ave)return;    if(idx<=0)return;    if(sum[idx]+num<=ave)    {        if(sum[idx]+num>ans)ans=sum[idx]+num;        return;    }    if(num>ans) ans=num;    dfs(idx-1,num+w[idx]);    dfs(idx-1,num);}int main(){    while(scanf("%d",&n)!=EOF)    {        int i,j;        ans=0;        for(i=1;i<=n;i++)scanf("%d",&w[i]),sum[i]=sum[i-1]+w[i];        ave=sum[n]>>1;        dfs(n,0);        printf("%d",sum[n]-2*ans);    }    return 0;}