Pass the Pillow — LeetCode 2582 Python Solution

The problem

There are n people standing in a line labeled from 1 to n. The first person in the line is holding a pillow initially.

Example

Input

n = 4, time = 5

Output

2

Explanation

People pass the pillow in the following way: 1 -> 2 -> 3 -> 4 -> 3 -> 2.

Python solution

class Solution:
    def passThePillow(self, n: int, time: int) -> int:
        ans = k = 1
        for _ in range(time):
            ans += k
            if ans == 1 or ans == n:
                k *= -1
        return ans

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 2582. Pass the Pillow 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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