[Swift Weekly Contest 111]LeetCode941. 有效的山脉数组 | Valid Mountain Array

Given an array A of integers, return true if and only if it is a valid mountain array.

Recall that A is a mountain array if and only if:

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

Example 1:

Input: [2,1]
Output: false

Example 2:

Input: [3,5,5]
Output: false

Example 3:

Input: [0,3,2,1]
Output: true

Note:

1. 0 <= A.length <= 10000
2. 0 <= A[i] <= 10000 

让我们回顾一下，如果 A 满足下述条件，那么它是一个山脉数组：

• A.length >= 3
• 在 0 < i < A.length - 1 条件下，存在 i 使得：
  • A[0] < A[1] < ... A[i-1] < A[i]
  • A[i] > A[i+1] > ... > A[B.length - 1]

示例 1：

输入：[2,1]
输出：false

示例 2：

输入：[3,5,5]
输出：false

示例 3：

输入：[0,3,2,1]
输出：true

提示：

1. 0 <= A.length <= 10000
2. 0 <= A[i] <= 10000 

 1 class Solution {
 2     func validMountainArray(_ A: [Int]) -> Bool {
 3         var n:Int = A.count
 4         if n < 3 {return false}
 5         var pre:Int = n - 1
 6         for i in 0..<(n - 1)
 7         {
 8             if A[i] >= A[i + 1]
 9             {
10                 pre = i
11                 break
12             }
13         }
14         if pre == 0 || pre == n-1 {return false}
15         for i in pre..<(n - 1)
16         {
17             if A[i] <= A[i + 1] {return false}
18         }
19         return true
20     }
21 }

原文地址：https://www.cnblogs.com/strengthen/p/9977686.html