代码

#include <algorithm>
#include <cstring>
#include <iostream>

using namespace std;

const int N = 1e5 + 10, M = 2e5 + 10;

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

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

bool dfs(int u, int c)
{
    color[u] = c;
    for (int i = h[u]; i != -1; i = ne[i]) {
        int j = e[i];
        if (!color[j]) {
            if (!dfs(j, 3 - c)) {
                return false;
            }
        }
        else if (color[j] == c) {
            return false;
        }
    }
    return true;
}

int main()
{
    cin >> n >> m;

    memset(h, -1, sizeof h);

    while (m--) {
        int a, b;
        cin >> 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;
                break;
            }
        }
    }
    if (flag) {
        puts("Yes");
    }
    else {
        puts("No");
    }
    return 0;
}