Codeforces Round #383 (Div. 1) C(二分图)

#include <iostream>
#include <cstdio>
#include <vector>
#define mp make_pair
#define fi first
#define se second
using namespace std;
const int maxn = 200050;
vector<int> G[maxn];
int color[maxn];
vector <pair <int, int>> Q;
void dfs(int x)
{
    for(auto to : G[x])
    {
        if(!color[to])
        {
            color[to] = color[x] == 1 ? 2 : 1;
            dfs(to);
        }
    }
}
int n, x, y;
int main()
{
    scanf("%d", &n);
    for(int i = 0; i < n; i++)
    {
        scanf("%d %d", &x, &y); x--; y--;
        G[x].push_back(y); G[y].push_back(x);
        Q.push_back(mp(x, y));
    }
    for(int i = 0; i < n; i ++)
        G[2*i].push_back(2*i+1), G[2*i+1].push_back(2*i);
    for(int i = 0; i < 2*n; i++)
        if(!color[i]) { color[i] = 1; dfs(i); }
    for(auto x : Q) printf("%d %d\n", color[x.fi], color[x.se]);
}