python/TangDou/AcWing/BipartiteGraph/860_bfs.cpp

#include <bits/stdc++.h>

using namespace std;
const int N = 100010, M = N << 1;
typedef pair<int, int> PII;

int n, m;
int color[N];
// 邻接表
int e[M], h[N], idx, ne[M];
void add(int a, int b) {
    e[idx] = b, ne[idx] = h[a], h[a] = idx++;
}
bool bfs(int x) {
    // 假设 1:黑，2：白，这样方便理解一些
    color[x] = 1;
    queue<PII> q;
    q.push({x, 1});
    while (q.size()) {
        PII t = q.front();
        q.pop();
        int u = t.first, c = t.second;
        for (int i = h[u]; ~i; i = ne[i]) {
            int v = e[i];
            if (!color[v]) {
                color[v] = 3 - c;
                q.push({v, 3 - c});
            } else if (color[v] == c) // 发现冲突
                return 0;
        }
    }
    return 1;
}

int main() {
    memset(h, -1, sizeof h);
    cin >> n >> m;
    int a, b;
    while (m--) {
        cin >> a >> b;
        add(a, b), add(b, a);
    }

    int flag = 1;
    for (int i = 1; i <= n; i++) {
        if (!color[i]) {
            if (!bfs(i)) {
                flag = 0;
                break;
            }
        }
    }
    if (flag)
        puts("Yes");
    else
        puts("No");
    return 0;
}