谁能告诉我我的代码问题在哪？

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>

using namespace std;

const int N = 5e6 + 5;

int n, m;
long long ans;
int fa[N], p[N], d[N];

long long TP() {
    for (int i = 1; i < n; i ++) scanf("%d", &fa[i]), ++ d[fa[i]];
    for (int i = 1, j = 1; i <= n - 2; i ++, j ++) {
        while (d[j]) j ++;
        p[i] = fa[j];
        while (i <= n - 2 && !--d[p[i]] && p[i] < j) {
            p[i + 1] = fa[p[i]];
            i ++;
        }
    }
    for (int i = 1; i <= n - 2; i ++) ans ^= 1LL * i * p[i];
    return ans;
}

long long PT() {
    for (int i = 1; i <= n - 2; i ++) scanf("%d", &p[i]), ++ d[p[i]];
    p[n - 1] = n;
    for (int i = 1, j = 1; i < n; i ++, j ++) {
        while (d[j]) j ++;
        fa[j] = p[i];
        while (i < n && !--d[fa[j]] && p[i] < j) {
            fa[p[i]] = p[i + 1];
            i ++;
        }
    }

    for (int i = 1; i < n; i ++) ans ^= 1LL * i * fa[i];
    return ans;
}

int main() {
    scanf("%d %d", &n, &m);
    printf("%lld\n", (m == 1 ? TP() : PT()));
    return 0;
}