MLE爆栈求解释

MLE（应该是爆栈）:

# include <bits/stdc++.h>

# define ffor(i,name) \
    for (auto i = name.begin (); i != name.end (); ++ i)

# define reg register

using namespace std;

typedef long long ll;

typedef pair <int, int> pii;

typedef pair <ll, ll> pll;

int n, m, f[10005], x, y, op;

int find (int x) {

    return x == f[x] ? x : f[x] = find (f[x]);

}

int main () {

    ios::sync_with_stdio (0);

    cin.tie (0);

    cout.tie (0);

    cin >> n >> m;

    for (reg int i = 1; i <= n; ++ i)
        f[i] = i;

    while (m --) {

        cin >> op >> x >> y;

        if (op < 2)
            f[find (x)] = y; //这里不一样
        else
            cout << (find (x) == find (y) ? "Y\n" : "N\n");

    }

    return 0;

}

AC:

# include <bits/stdc++.h>

# define ffor(i,name) \
    for (auto i = name.begin (); i != name.end (); ++ i)

# define reg register

using namespace std;

typedef long long ll;

typedef pair <int, int> pii;

typedef pair <ll, ll> pll;

int n, m, f[10005], x, y, op;

int find (int x) {

    return x == f[x] ? x : f[x] = find (f[x]);

}

int main () {

    ios::sync_with_stdio (0);

    cin.tie (0);

    cout.tie (0);

    cin >> n >> m;

    for (reg int i = 1; i <= n; ++ i)
        f[i] = i;

    while (m --) {

        cin >> op >> x >> y;

        if (op < 2)
            f[find (x)] = find (y); //这里不一样
        else
            cout << (find (x) == find (y) ? "Y\n" : "N\n");

    }

    return 0;

}

为啥啊