Cod sursă (job #420345)

#include<bits/stdc++.h>
#define N 503
using namespace std;

int dx[]={-1,-1,0,1,1,0};
int dy[]={0,1,1,0,-1,-1};

int t,x,y,n;
short int a[N][N];
int p[2][N*N];
int c[N][N];
bool d[2][N*N+5][3];
bool u;

bool OK(int i, int j) {
    return (i>=1 && j>=1 && i<=n && j<=n);
}
bool v;
int find(int x, bool u) {
    if (p[u][x]==x) return x;
    else return (p[u][x]=find(p[u][x], u));
}

int main() {
    ifstream cin("hex.in");
    ofstream cout("hex.out");
    cin>>n;

    for(int i=1; i<=n; ++i)
        for (int j=1; j<=n; ++j) {
            c[i][j]=(i-1)*n+j;
            p[0][c[i][j]]=p[1][c[i][j]]=c[i][j];
            a[i][j]=10;
        }//0 rosie 1 albastru


    for (int i=1; i<=n*n; ++i) {
        cin>>x>>y;
        if (i%2) u=0;
        else u=1;
        a[x][y]=u;

        int a1=find(c[x][y], u);
        if (i%2) {
            if  (y==1) d[u][a1][0]=1;
            if (y==n) d[u][a1][1]=1;
        } else {
            if (x==1) d[u][a1][0]=1;
            if (x==n) d[u][a1][1]=1;
        }
        if (d[u][a1][0] && d[u][a1][1]) {
            cout<<i;
            return 0;
        }

        for (int d1=0; d1<6; ++d1) {
            int i2=x+dx[d1];
            int j2=y+dy[d1];
            if (!OK(i2,j2) || a[i2][j2]!=u) continue;
            int b=find(c[i2][j2], u);
            a1=find(c[x][y], u);
            if (b!=a1) {
                p[u][b]=a1;
                d[u][a1][0]=max(d[u][a1][0], d[u][b][0]);
                d[u][a1][1]=max(d[u][a1][1], d[u][b][1]);
            }

        }
        a1=find(c[x][y], u);
        if (d[u][a1][0] && d[u][a1][1]) {
            cout<<i;
            return 0;
        }

    }

    return 0;
}