Problem p03822 (python)

Fixed submission:
# -*- coding: utf-8 -*-
import resource
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(10000000)
input = sys.stdin.readline
INF = 2**62-1

def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


g = defaultdict(list)


def f(u):
    d = [f(v) for v in g[u]]
    if not d:
        return 0

    d.sort(reverse=True)
    while len(d) > 1:
        l = d.pop()
        r = d.pop()
        d.append(max((l + 1, r)))
    return d[0] + 1

@mt
def slv(N, A):
    global g
    for i, a in enumerate(A):
        i += 2
        g[a].append(i)

    return f(1)


def main():
    N = read_int()
    A = [read_int() for _ in range(N-1)]
    print(slv(N, A))


if __name__ == '__main__':
    main()

Buggy submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)
input = sys.stdin.readline
INF = 2**62-1

def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


@mt
def slv(N, A):
    g = defaultdict(list)
    for i, a in enumerate(A):
        i += 2
        g[a].append(i)

    @lru_cache(maxsize=None)
    def f(u):
        d = []
        for v in g[u]:
            d.append(f(v))

        if not d:
            return 0

        heapq.heapify(d)
        while len(d) > 1:
            l = heapq.heappop(d)
            r = heapq.heappop(d)
            heapq.heappush(d, max((l + 1, r)))
        return heapq.heappop(d) + 1
    return f(1)


def main():
    N = read_int()
    A = [read_int() for _ in range(N-1)]
    print(slv(N, A))


if __name__ == '__main__':
    main()