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LeetCode solutions

1185. Find in Mountain Array

My accepted Python solution to LeetCode problem 1185, Find in Mountain Array, running in 28ms.

  • Difficulty: Hard
  • Python
  • Runtime 28ms
  • Memory 18.5MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 28ms, memory 18.5MB, accepted 2026-01-02.

python
# """
# This is MountainArray's API interface.
# You should not implement it, or speculate about its implementation
# """
#class MountainArray:
#    def get(self, index: int) -> int:
#    def length(self) -> int:

class Solution:
    def findInMountainArray(self, target: int, mountain_arr: 'MountainArray') -> int:
        n = mountain_arr.length()
        
        # Find peak
        left, right = 0, n - 1
        while left < right:
            mid = (left + right) // 2
            if mountain_arr.get(mid) < mountain_arr.get(mid + 1):
                left = mid + 1
            else:
                right = mid
        peak = left
        
        # Binary search in ascending part
        left, right = 0, peak
        while left <= right:
            mid = (left + right) // 2
            val = mountain_arr.get(mid)
            if val == target:
                return mid
            elif val < target:
                left = mid + 1
            else:
                right = mid - 1
        
        # Binary search in descending part
        left, right = peak, n - 1
        while left <= right:
            mid = (left + right) // 2
            val = mountain_arr.get(mid)
            if val == target:
                return mid
            elif val > target:
                left = mid + 1
            else:
                right = mid - 1
        
        return -1

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