染色法判定二分图

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

const int N = 100010;

int h[N], e[N], ne[N], w[N], idx;

int color[N];
int n, m;

void add(int a, int b, int c) {
    e[idx] = b, w[idx] = c, 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(color[j] == c) return false;
        } else {
            if(!dfs(j,3-c)) return false;
        }
    }
    return true;
}

int main() {
    scanf("%d%d",&n,&m);
    memset(h,-1,sizeof h);
    while(m -- ) {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        add(a,b,c),add(b,a,c);
    }
    bool flag = true;
    for(int i = 1; i <= n; i++) {
        if(color[i]) continue;
        if(!dfs(i,1)) {
            flag = false;
            break;
        } 
    }
    if(flag) puts("Yes");
    else puts("No");
    return 0;
}