Ladders

import sys
from collections import deque, defaultdict, Counter
from heapq import heappush, heappop, heapify
from bisect import bisect_left, bisect_right
from itertools import permutations, combinations, product, accumulate, groupby
from functools import lru_cache, cmp_to_key, reduce
from math import gcd, isqrt, comb, inf, pi, sqrt, atan2, hypot


def main():
    data = sys.stdin.buffer.read().split(); idx = 0
    n = int(data[idx]); idx += 1
    a = list(map(int, data[idx:idx + n])); idx += n

    idx_of_the_num = [0]*(n+1)
    for i in range(n):
        idx_of_the_num[a[i]] = i


    # time_to_get = [n+1 for i in range(n)]
    # time_to_get[0] = 0


    # h = [(0,0)]
    # while h:
    #     new_t, i = heappop(h)
    #     t = time_to_get[i]
    #     val = a[i]

    #     if i+1 < n and time_to_get[i+1] > t+1:
    #         time_to_get[i+1] = t+1
    #         heappush(h, (t+1, i+1))

    #     jump_val = val + val
    #     while jump_val <= n:
    #         idx = idx_of_the_num[jump_val]
    #         if time_to_get[idx] > t+1:
    #             time_to_get[idx] = t+1
    #             heappush(h, (t+1, idx))

    #         jump_val += val

    time_to_get = [-1] * n
    time_to_get[0] = 0

    q = deque([0])
    while q:
        i = q.popleft()
        t = time_to_get[i] + 1

        nxt = [idx_of_the_num[m] for m in range(2 * a[i], n + 1, a[i])]
        if i + 1 < n:
            nxt.append(i + 1)

        for j in nxt:
            if time_to_get[j] < 0:
                time_to_get[j] = t
                q.append(j)



    print(time_to_get[-1])

main()

Test 1

Verdict: ACCEPTED

Test 2

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Test 3

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Test 4

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Test 5

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Test 68

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Test 69

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Test 70

Verdict: ACCEPTED

Test 71

Verdict: ACCEPTED