Make it Increasing (Codeforces 1668C)
Tags: Greedy, brute force

You are given an array $$$a$$$ consisting of $$$n$$$ positive integers, and an array $$$b$$$, with length $$$n$$$. Initially $$$b_i=0$$$ for each $$$1 \leq i \leq n$$$.In one move you can choose an integer $$$i$$$ ($$$1 \leq i \leq n$$$), and add $$$a_i$$$ to $$$b_i$$$ or subtract $$$a_i$$$ from $$$b_i$$$. What is the minimum number of moves needed to make $$$b$$$ increasing (that is, every element is strictly greater than every element before it)?

Input: The first line contains a single integer $$$n$$$ ($$$2 \leq n \leq 5000$$$).The second line contains $$$n$$$ integers, $$$a_1$$$, $$$a_2$$$, ..., $$$a_n$$$ ($$$1 \leq a_i \leq 10^9$$$) — the elements of the array $$$a$$$.

Output: Print a single integer, the minimum number of moves to make $$$b$$$ increasing.

Note: Example $$$1$$$: you can subtract $$$a_1$$$ from $$$b_1$$$, and add $$$a_3$$$, $$$a_4$$$, and $$$a_5$$$ to $$$b_3$$$, $$$b_4$$$, and $$$b_5$$$ respectively. The final array will be [$$$-1$$$, $$$0$$$, $$$3$$$, $$$4$$$, $$$5$$$] after $$$4$$$ moves.Example $$$2$$$: you can reach [$$$-3$$$, $$$-2$$$, $$$-1$$$, $$$0$$$, $$$1$$$, $$$2$$$, $$$3$$$] in $$$10$$$ moves.

Sample Inputs:
5
1 2 3 4 5

7
1 2 1 2 1 2 1

8
1 8 2 7 3 6 4 5

Sample Outputs:
4

10

16

Solution (Python):
def main():
    n = int(input())
    a = list(map(int, input().split()))
    ans = -1
    for s in range(n):
        an = 0
        v = 0
        for i in reversed(range(s)):
            x = int(v / a[i]) + 1
            an += x
            v = x * a[i]
        v = 0
        for i in range(s + 1, n):
            x = int(v / a[i]) + 1
            an += x
            v = x * a[i]
        if ans == -1 or an < ans:
            ans = an
    print(ans)
main()

Solution (Python):
n = int(input())
l = list(map(int, input().split()))
answer = None
for Pythonic__Python in range(n):
    (ppre, npre, c) = (0, 0, 0)
    for j in range(Pythonic__Python - 1, -1, -1):
        x = int(ppre / l[j]) + 1
        c += x
        ppre = l[j] * x
    for k in range(Pythonic__Python + 1, n):
        x = int(npre / l[k]) + 1
        c += x
        npre = l[k] * x
    if answer == None:
        answer = c
    else:
        answer = min(answer, c)
print(answer)

Solution (Python):
n = int(input())
l = list(map(int, input().split()))
answer = None
for i in range(n):
    (ppre, npre, c) = (0, 0, 0)
    for j in range(i - 1, -1, -1):
        x = int(ppre / l[j]) + 1
        c += x
        ppre = l[j] * x
    for k in range(i + 1, n):
        x = int(npre / l[k]) + 1
        c += x
        npre = l[k] * x
    if answer == None:
        answer = c
    else:
        answer = min(answer, c)
print(answer)