Peak-Index-in-a-Mountain-Array

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题目地址

LeetCode#852 Peak Index in a Mountain Array

题目描述

  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:

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

Example 2:

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

Note:

  1. 3 <= A.length <= 10000
  2. 0 <= A[i] <= 10^6
  3. A is a mountain, as defined above.

解题思路

  直接遍历。。。

解题代码

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class Solution {
public:
    int peakIndexInMountainArray(vector<int>& A) {
        if (A.size() < 3) return 0;
        for (int i = 1; i < A.size(); ++i) {
            if (A[i] < A[i-1]) return i-1;
        }
        return 0;
    }
};
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