Codeforces687A - NP-Hard Problem（二分图染色）

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题目链接

http://codeforces.com/contest/687/problem/A

思路

只需要将这个图二分染色，然后输出解即可

代码

#include <iostream>#include <cstring>#include <stack>#include <vector>#include <set>#include <map>#include <cmath>#include <queue>#include <sstream>#include <iomanip>#include <fstream>#include <cstdio>#include <cstdlib>#include <climits>#include <deque>#include <bitset>#include <algorithm>using namespace std;#define PI acos(-1.0)#define LL long long#define PII pair<int, int>#define PLL pair<LL, LL>#define mp make_pair#define IN freopen("in.txt", "r", stdin)#define OUT freopen("out.txt", "wb", stdout)#define scan(x) scanf("%d", &x)#define scan2(x, y) scanf("%d%d", &x, &y)#define scan3(x, y, z) scanf("%d%d%d", &x, &y, &z)#define sqr(x) (x) * (x)const int maxn = 100000 + 5;vector<int> G[maxn];int n, m, color[maxn];vector<int> ans1, ans2;bool bicolor(int u) {    for (int i = 0; i < G[u].size(); i++) {        int v = G[u][i];        if (color[v] == color[u]) return false;        if (!color[v]) {            color[v] = 3 - color[u];            if (!bicolor(v)) return false;        }    }    return true;}int main() {    scan2(n, m);    for (int i = 0; i < m; i++) {        int x, y;        scan2(x, y);        G[x].push_back(y);        G[y].push_back(x);    }    bool flag = true;    for (int i = 1; i <= n; i++) {        if (!color[i]) {            color[i] = 1;            if (!bicolor(i)) flag = false;;        }    }    if (!flag) printf("-1\n");    else {        for (int i = 1; i <= n; i++) {            if (color[i] == 1) ans1.push_back(i);            if (color[i] == 2) ans2.push_back(i);        }        printf("%d\n", ans1.size());        for (int i = 0; i < ans1.size(); i++) printf("%d ", ans1[i]);        printf("\n%d\n", ans2.size());        for (int i = 0; i < ans2.size(); i++) printf("%d ", ans2[i]);        printf("\n");    }    return 0;}

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