题意

题目链接

Sol

说实话这题我到现在都不知道咋A的。

考试的时候是对任意相邻点之间连边，然后一分没有

然后改成每两个之间连一条边就A了。。

按说是可以过掉任意坐标上的点都是偶数的数据啊。。

#include<cstdio>

#include<algorithm>

#include<iostream>

#include<vector>

#include<cstring>

#include<queue>

#define Pair pair<int, int>

#define MP(x, y) make_pair(x, y)

#define fi first

#define se second

using namespace std;

const int MAXN = 2e5 + 10, INF = 1e9 + 10, mod = 998244353;

inline int read() {

    char c = getchar(); int x = 0, f = 1;

    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}

    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();

    return x * f;

}

int N;

int x[MAXN], y[MAXN], date[MAXN], numx[MAXN], numy[MAXN];

vector<int> E[MAXN];

vector<Pair> tmp[MAXN];

void Get(int *a) {

    for(int i = 1; i <= N; i++) date[i] = a[i];

    sort(date + 1, date + N + 1);

    int num = unique(date + 1, date + N + 1) - date - 1;

    for(int i = 0; i <= num; i++) tmp[i].clear();

    for(int i = 1; i <= N; i++) a[i] = lower_bound(date + 1, date + num + 1, a[i]) - date - 1, tmp[a[i]].push_back(MP(a[i], i));

    for(int i = 0; i <= num; i++) {

        if(tmp[i].size() < 2) continue;

        sort(tmp[i].begin(), tmp[i].end());

        for(int j = 0; j < tmp[i].size() - 1; j += 2) {

            int x = tmp[i][j].se, y = tmp[i][j + 1].se;

            E[x].push_back(y);

            E[y].push_back(x);

        }

    }

}

int vis[MAXN], vis2[MAXN];

void BFS(int k) {

    queue<int> q;

    vis[k] = 1; q.push(k);

    while(!q.empty()) {

        int p = q.front(); q.pop();

        if(vis2[p]) continue; vis2[p] = 1;

        for(int i = 0; i < E[p].size(); i++) {

            int to = E[p][i];

            vis[to] = vis[p] ^ 1;

            q.push(to);

        }

    }

}

int main() {

    N = read();

    for(int i = 1; i <= N; i++) x[i] = read(), y[i] = read();

    Get(x); Get(y);

    for(int i = 1; i <= N; i++) if(!vis2[i]) BFS(i);

    for(int i = 1; i <= N; i++) putchar(vis[i] == 0 ? 'b' : 'r');

    return 0;

}