AcWing 860. 染色法判定二分图（二分图判断模板）

题目链接：860. 染色法判定二分图 - AcWing题库

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题目大意：

给定一个 n 个点 m 条边的无向图，图中可能存在重边和自环。

请你判断这个图是否是二分图。

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代码：

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<vector>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<unordered_set>
#include<unordered_map>
#include<bitset>
#include<tuple>
#define inf 72340172838076673
#define int long long
#define endl '\n'
#define F first
#define S second
#define  mst(a,x) memset(a,x,sizeof (a))
using namespace std;
typedef pair<int, int> pii;

const int N = 200086, mod = 998244353;

int n, m;
int h[N], ne[N], e[N], idx;
int col[N];

void add(int a, int b) {
    e[idx] = b;
    ne[idx] = h[a];
    h[a] = idx++;
}

bool dfs(int u, int c) {

    col[u] = c;
    for (int i = h[u]; ~i; i = ne[i]) {
        int j = e[i];
        if (!col[j]) {
            if (!dfs(j, 3 - c)) return false;
        } else if (col[j] == c) return false;
    }
    
    return true;
}

void solve() {

    mst(h, -1);
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int a, b;
        cin >> a >> b;
        add(a, b), add(b, a);
    }
    
    bool ok = false;
    for (int i = 1; i <= n; i++) {
        if (!col[i]) {
            if (!dfs(i, 1)) ok = true;
        }
    }
    
    if (ok) cout << "No" << endl;
    else cout << "Yes" << endl; 
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    
    int T = 1;
// cin >> T;
    while (T--) solve();
    
    return 0;
}