poi 1182

食物链 || 带权并查集

0：同类

1：吃

2：被吃

#include <cstdio>
using namespace std;
const int maxn=5e4+3;

int f[maxn], w[maxn];

void init(int n)
{
    for(int i = 1; i <= n; ++i) f[i] = i, w[i] = 0;
}

int find(int x)
{
    if(x == f[x]) return x;
    int tmp = f[x];
    f[x] = find(f[x]);
    w[x] = (w[x] + w[tmp] + 3) % 3;//这里其实不用+3，因为w[i]为0-2的数
    return f[x];
}

int main()
{
    int n, k, d, x, y, cnt = 0;
    scanf("%d %d", &n, &k);
    init(n);
    for(int i = 0; i < k; ++i)
    {
        scanf("%d %d %d", &d, &x, &y);
        if(x > n || y > n || (d == 2 && x == y))
        {
            ++cnt; continue;
        }
        int xx = find(x), yy = find(y);
        if(xx == yy)
        {
            if((w[x] - w[y] + 3) % 3 != d - 1) ++cnt;
        }
        else
        {
            f[xx] = yy;
            w[xx] = (w[y] - w[x] + d - 1 + 3) % 3;
        }
    }
    printf("%d\n", cnt);
}