Number of Ways to Buy Pens and Pencils — LeetCode 2240 Python Solution

The problem

You are given an integer total indicating the amount of money you have. You are also given two integers cost1 and cost2 indicating the price of a pen and pencil respectively.

Example

Input

total = 20, cost1 = 10, cost2 = 5

Output

9

Explanation

The price of a pen is 10 and the price of a pencil is 5.

Python solution

class Solution:
    def waysToBuyPensPencils(self, total: int, cost1: int, cost2: int) -> int:
        ans = 0
        for x in range(total // cost1 + 1):
            y = (total - (x * cost1)) // cost2 + 1
            ans += y
        return ans

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 2240. Number of Ways to Buy Pens and Pencils is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

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