POJ 1011 Sticks（dfs+剪枝）

////  main.cpp//  Richard////  Created by 邵金杰 on 16/8/31.//  Copyright © 2016年 邵金杰. All rights reserved.//#include<iostream>#include<cstdio>#include<vector>#include<cstring>#include<algorithm>using namespace std;vector<int> stick;const int maxn=1000+10;int vis[maxn];int n;int totlen=0,L;int nlastNo;bool dfs(int n,int m){    if(n==0&&m==0) return true;    if(m==0) m=L;    int nstartNo=0;    if(m!=L) nstartNo=nlastNo+1;    for(int i=nstartNo;i<stick.size();i++)    {        if(!vis[i]&&stick[i]<=m)        {            if(i>0&&vis[i-1]==0&&stick[i]==stick[i-1]) continue;            vis[i]=1;nlastNo=i;            if(dfs(n-1,m-stick[i])){                return true;            }            else {                vis[i]=0;                if(stick[i]==m||m==L) return false;            }        }    }    return false;}int main(){    int slen;    while(scanf("%d",&n)&&n)    {        totlen=0;        stick.clear();        for(int i=0;i<n;i++)        {            scanf("%d",&slen);            totlen+=slen;            stick.push_back(slen);        }        sort(stick.begin(),stick.end(),greater<int>());        for(L=stick[0];L<=totlen/2;L++)        {            if(totlen%L) continue;            memset(vis,0,sizeof(vis));            if(dfs(n,L))            {                cout<<L<<endl;                break;            }        }        if(L>totlen/2) cout<<totlen<<endl;    }    return 0;}