Leetcode: Peak Index in a Mountain Array

Peak Index in a Mountain Array



Similar Problems:


Let’s call an array A a mountain if the following properties hold:

  • A.length >= 3
  • There exists some 0 < i < A.length – 1 such that A[0] < A[1] < … A[i-1] < A[i] > A[i+1] > … > A[A.length – 1]

Given an array that is definitely a mountain, return any i such that A[0] < A[1] < … A[i-1] < A[i] > A[i+1] > … > A[A.length – 1].

Example 1:

Input: [0,1,0]
Output: 1

Example 2:

Input: [0,2,1,0]
Output: 1

Note:

  • 3 <= A.length <= 10000
  • 0 <= A[i] <= 10^6
  • A is a mountain, as defined above.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


  • Solution:
// Blog link: https://code.dennyzhang.com/peak-index-in-a-mountain-array
// Basic Ideas: Too straightforward
// Complexity: Time O(n), Space O(1)
func peakIndexInMountainArray(A []int) int {
    for i:=1; i<len(A)-1; i++ {
        if A[i]>A[i-1] && A[i]>A[i+1] {
            return i
        }
    }
    return -1
}
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