染色法二分图

#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10, M = 1e5 + 10, INF = 0x3f3f3f3f;
int n, m, h[N], e[M << 1], ne[M << 1], idx, color[N];

void addEdge(int f, int t)
{
    e[idx] = t, ne[idx] = h[f], h[f] = idx ++ ;
}

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

int main()
{
    cin >> n >> m;
    memset(h, -1, sizeof h);
    for(int i = 0; i < m; i ++ )
    {
        int f, t;
        cin >> f >> t;
        addEdge(f, t);
        addEdge(t, f);
    }

    bool flag = true;

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

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

    return 0;
}