实在不明白为什么没结果，还请各位帮帮忙 指点一下
#include "stdafx.h"
#include<iostream>
#include<set>
#include"compare.h"
#include<queue>
#include<cmath>
#define M 20
#define N 2

using namespace std;

int main()
{
    int coordinate[20][2]={
        {55,34},{22,44},{23,43},{24,25},{12,55},{66,32},{78,13},{90,56},{66,43},{23,45},
        {33,78},{90,56},{34,56},{24,76},{23,88},{52,75},{65,43},{32,76},{73,46},{21,23}
                           };
    int i,j,k,h,l,chance,turn,sum,g;
    int flag[M]={};
    int mark[M]={};
    for(turn=0;turn<3;turn++)
    {
        sum=0;
        cout<<endl;
        for(h=0;h<M;h++)
       {
           chance=0;
           if(flag[h]==0)
           {
               for(j=0;j<M;j++)
               {
                   k=0;
                   for(i=0;i<N;i++)
                   {
                       if(flag[j]==0&&h!=j)
                       {
                           if(compare(coordinate[h][i],coordinate[j][i])==2)
                              k++;
                       }
                       else
                           break;
                   }
                   if(k==0)
                       chance++;
               }
               if(chance==0)
               {
                   mark[sum]=h;
                   sum++;
                   for(l=0;l<N;l++)
                   {
                       cout<<coordinate[h][l]<<" ";
                   }
                   cout<<endl;
               }
           }
        }
        for(g=0;g<sum;g++)
        {
            flag[mark[g]]=1;
        }
    }
   
}
函数compare(int a,int b)的定义
int compare(int a,int b);

using namespace std;

int compare(int a,int b)
{
    int x;
    if(a>b)
        x=2;
    if(a=b)
        x=1;
    if(a<b)
        x=0;
    return(x);
}

这个程序是在Microsoft Visual Studio 2008中运行的 不知道在其他的软件中运行会不会出错