2023-9-2 染色法判定二分图

题目链接：染色法判定二分图

#include 
#include 
#include 

using namespace std;

const int N = 100010l, M = 200010;

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])
        {
            // 进行染色
            if(!dfs(i, 1))
            {
                flag = false;
                break;
            }
        }
    }
    
    if(flag) cout << "Yes" << endl;
    else cout << "No" << endl;
    
    return 0;
}