HackerRank Construct the Array

解答

code: python

import math

import os

import random

import re

import sys

# Complete the 'countArray' function below.

# The function is expected to return a LONG_INTEGER.

# The function accepts following parameters:

# 1. INTEGER n

# 2. INTEGER k

# 3. INTEGER x

def countArray(n, k, x):

# Return the number of ways to fill in the array.

MOD = 1000000007

a = 0 * n

b = 0 * n

a0 = 1 if x == 1 else 0

b0 = 0 if x == 1 else 1

for i in range(1, n):

ai = bi-1 % MOD

bi = (ai-1 * (k-1) + bi-1 * (k-2)) % MOD

return an-1

if __name__ == '__main__':

fptr = open(os.environ'OUTPUT_PATH', 'w')

first_multiple_input = input().rstrip().split()

n = int(first_multiple_input0)

k = int(first_multiple_input1)

x = int(first_multiple_input2)

answer = countArray(n, k, x)

fptr.write(str(answer) + '\n')

fptr.close()

メモ

https://www.youtube.com/watch?v=_nLeiMMSd4E

bi-1

https://scrapbox.io/files/61d24246effe30001d3a4450.png