染色法判断二分图模板

C++ 代码

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int n = 100100, m = 3 * n;

int h[n], ne[m], to[m],e[m],idx;


int color[n];

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

bool dfs(int fa,int col)
{
    color[fa] = col;
    for (int i = h[fa]; ~i; i = ne[i])
    {
        int j = e[i];
        if (!color[j])
        {
            if (!dfs(j, 3 - col))
                return false;
        }
        else if(color[j]==col)
        {
            return false;
        }
    }
    return true;
}
int N, M;
int main()
{
    memset(h,-1,sizeof h);
    scanf("%d %d", &N, &M);


    for (int i = 0; i < M; i++)
    {
        int a, b;
        scanf("%d%d", &a, &b);
        addedge(a, b), addedge(b, a);
    }
    bool flag = true;
    for (int i = 0; i <= n; i++)
    {
        if (!color[i])
        {
            if (dfs(i, 1) == false)
            {
                flag = false;
                break;
            }
        }


    }

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




    return 0;
}