Description:
Let’s call an array A a mountain if the following properties hold:
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:
Example 2:
Note:
- 3 <= A.length <= 10000
- 0 <= A[i] <= 10^6
- A is a mountain, as defined above.
题意:给定一个一维数组,要求找出位置i(0 < i < A.length - 1),另其满足 A[0] < A[1] < … A[i-1] < A[i] > A[i+1] > … > A[A.length - 1];
解法:对于位置i左边和右边的元素来说,是已经排好序的了,因此我们可以利用二分查找法,定义left = 0, right = A.length - 1,mid = (left + right) /2 ;找到满足A[mid] > A[mid - 1] && A[mid] > A[mid + 1]的那个位置;
Java