题目链接：食物链

#include <iostream>

using namespace std;

const int N = 50010;

int n, m;
int p[N], d[N];

int find(int x)
{
    if(p[x] != x)
    {
        int t = find(p[x]);
        d[x] += d[p[x]];
        p[x] = t;
    }
    return p[x];
}

int main()
{
    cin >> n >> m;
    
    for(int i = 1; i <= n; i++) p[i] = i;
    
    int res = 0;
    while(m --)
    {
        int t, x ,y;
        cin >> t >> x >> y;
        int px = find(x), py = find(y);
        
        if(x > n || y > n) res ++;
        else
        {
            if(t == 1)
            {
                if(px == py && (d[x] - d[y]) % 3) res++;
                else if(px != py)
                {
                    p[px] = py;
                    d[px] = d[y] - d[x];
                }
            }
            else
            {
                if(px == py && (d[x] - 1 - d[y]) % 3) res ++;
                else if(px != py)
                {
                    p[px] = py;
                    d[px] = d[y] - d[x] + 1;
                }
            }
        }
    }
    cout << res << endl;
}