染色法判定二分图 模板题

#include <bits/stdc++.h>
using namespace std;

const int N = 100005;

struct {
    int to;
    int nxt;
}edges[N << 1];

int head[N], cnt = 0;
int n, m;

int color[N];

void add(int u, int v)
{
    edges[++cnt].to = v;
    edges[cnt].nxt = head[u];
    head[u] = cnt;
}

bool dfs(int v, int t)
{
    color[v] = t;
    for (int e = head[v]; e != 0; e = edges[e].nxt) {
        if (!color[edges[e].to]) {
            if (!dfs(edges[e].to, 3 - t))
                return false;
        }
        else {
            if (color[edges[e].to] == t)
                return false;
        }
    }

    return true;
}

int main() 
{
#ifndef ONLINE_JUDGE
    freopen("D:/VS CODE/C++/in.txt", "r", stdin);
    freopen("D:/VS CODE/C++/out.txt", "w", stdout);
#endif
    cin >> n >> m;

    for (int i = 0; i < m; ++i) {
        int a, b;
        scanf("%d %d", &a, &b);
        add(a, b);
        add(b, a);
    }
    
    bool flag = true;

    for (int i = 1; i <= n; ++i) {
        if (!color[i]) {
           if(!dfs(i, 1)) {
               flag = false;
           }
        }
    }

    if (flag)
        puts("Yes");
    else
    {
        puts("No");
    }
    

    fclose(stdin);
    fclose(stdout);
    return 0;
}