Cod sursă (job #770758)

#include<bits/stdc++.h>
using namespace std;
int n,x,y,x2,y2,b[25005];char a[505][505];
int d1[]={1,0,-1,0,-1,1},d2[]={0,1,0,-1,1,-1};
bool c[4][25005],check;
int unire(int x){
    if(b[x]==0)return x;
    return b[x]=unire(b[x]);
}
int main(){
    ifstream cin("hex.in");
    ofstream cout("hex.out");
    cin>>n;
    for(int i=1;i<=n*n;i++){
        cin>>x>>y;
        x2=unire(x*(n+1)+y);
        if(x==1)c[0][x2]=1;
        if(x==n)c[1][x2]=1;
        if(y==1)c[2][x2]=1;
        if(y==n)c[3][x2]=1;
        if(i%2==1)a[x][y]='r';else a[x][y]='a';
        for(int j=0;j<=5;j++)
            if(a[x+d1[j]][y+d2[j]]==a[x][y]){
                y2=unire((x+d1[j])*(n+1)+y+d2[j]);
                if(x2!=y2){
                    b[y2]=x2;
                    for(int l=0;l<=3;l++)
                        if(c[l][y2])c[l][x2]=1;else if(c[l][x2])c[l][y2]=1;
                }
            }
        if((i%2&&c[0][x2]&&c[1][y2])||(i%2&&c[2][x2]&&c[3][x2])){
            cout<<i<<endl;
            check=1;
        }
        if(check)break;
    }
    return 0;
}