LeetCode #852 - Peak Index in a Mountain Array

最新推荐文章于 2021-10-11 08:25:11 发布

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本文介绍了一种高效算法，用于在特定类型的数组（山形数组）中找到峰值的位置。通过使用二分查找策略，该算法能够在对数时间内确定数组中的最高点。

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题目描述：

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

• A.length >= 3

• There exists some 0 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:

1. 3 <= A.length <= 10000

2. 0 <= A[i] <= 10^6

3. A is a mountain, as defined above.

class Solution {
public:
    int peakIndexInMountainArray(vector<int>& A) {
        int begin=0;
        int end=A.size()-1;
        while(begin<end)
        {
            int mid=(begin+end)/2;
            if(A[mid]<A[mid+1]) begin=mid+1;
            else end=mid;
        }
        return begin;
    }
};