poj 2454 Jersey Politics

http://poj.org/problem?id=2454

随机化 

先从大到小排序 最后k个舍去

把前2×k个分成两组然后不断交换两组的第随机产生个 元素

知道满足条件

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<queue>
#include<cstring>
#include<set>
#include<cmath>
#include<algorithm>

using namespace std;

const int N=605;
struct node
{
    int I;
    int num;
}cow[N];
bool had[N];
bool cmp(node a,node b)
{
    return a.num>b.num;
}
int main()
{
    freopen("data.txt","r",stdin);
    srand((unsigned)time(NULL));
    int n;
    //while(scanf("%d",&n)!=EOF)
    {
        scanf("%d",&n);
        for(int i=0;i<n*3;++i)
        {
            scanf("%d",&cow[i].num);
            cow[i].I=i+1;
        }
        sort(cow,cow+n*3,cmp);
        int sum1=0;
        int sum2=0;
        for(int i=0;i<n;++i)
        sum1+=cow[i].num;
        for(int i=n;i<n*2;++i)
        sum2+=cow[i].num;
        while(1)
        {
            if(sum1>n*500&&sum2>n*500)
            break;
            int i=rand()%n;
            int j=rand()%n+n;
            sum1=sum1-cow[i].num+cow[j].num;
            sum2=sum2-cow[j].num+cow[i].num;
            swap(cow[i].I,cow[j].I);
            swap(cow[i].num,cow[j].num);
        }
        for(int i=0;i<n*3;++i)
        printf("%d\n",cow[i].I);
    }
    return 0;
}