POJ 1011 Sticks (backtrakcing+剪枝)

POJ  1011  Sticks    backtrakcing+剪枝

#include <iostream>#include <vector>#include <cstdio>#include <cmath>#include <algorithm>using namespace std;int n,sum,maxx,marked,visited[100],ans;vector <int> v;void initial(){v.clear();sum=0;maxx=0;marked=0;for(int i=0;i<100;i++) visited[i]=-1;}bool cmp(int a,int b){return a>b;} void input(){int x;for(int i=0;i<n;i++){scanf("%d",&x);v.push_back(x);sum+=x;maxx=max(maxx,x);}sort(v.begin(),v.end(),cmp);}bool dfs(int cnt,int x,int pos){if(cnt==0) return true;else if(x==0) return dfs(cnt-1,ans,-1);else{for(int i=pos+1;i<v.size();i++){if(x>=v[i] && visited[i]!=marked){visited[i]=marked;if( dfs(cnt,x-v[i],i) ) return true;else{visited[i]=marked-1;if( v[i]==x || x==ans) return false;//剪枝的核心} }}return false;}}void computing(){for(int i=maxx;i<=sum/2;i++){if(sum%i==0){marked++;ans=i;if(dfs(sum/i,i,-1)){cout<<ans<<endl;return;}}}cout<<sum<<endl; }int main(){while(scanf("%d",&n)!=EOF && n){initial();input();computing();}return 0;}