Cod sursă (job #542630)

#include<bits/stdc++.h>
using namespace std;
int n,x,y,x2,y2,b[253005];
char a[1000][1000];
int d1[]={0,1,0,-1,1,-1},d2[]={1,0,-1,0,-1,1};
bool c[4][253005],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<6;++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<4;++l)
                        if(c[l][y2])c[l][x2]=1;else if(c[l][x2])c[l][y2]=1;
                }
            }
        if(((i%2==0)&&c[0][x2]&&c[1][x2])||(i%2&&c[2][x2]&&c[3][x2])){
            cout<<i;
            return 0;
        }
    }
}