896. Monotonic Array

Easy
​
An array is monotonic if it is either monotone increasing or monotone decreasing.
An array nums is monotone increasing if for all i <= j, nums[i] <= nums[j]. An array nums is monotone decreasing if for all i <= j, nums[i] >= nums[j].
Given an integer array nums, return true if the given array is monotonic, or false otherwise.
Example 1:
Input: nums = [1,2,2,3]
Output:
true
Example 2:
Input: nums = [6,5,4,4]
Output:
true
Example 3:
Input: nums = [1,3,2]
Output:
false
Constraints:
  • 1 <= nums.length <= 105
  • -105 <= nums[i] <= 105

解題

O(n)
Runtime: 152 ms, faster than 85.47%
Memory Usage: 9.2 MB, less than 77.78%
func isMonotonic(nums []int) bool {
if len(nums)==1 { return true }
for i:=1; i<len(nums); i++ {
if nums[i]<nums[i-1] {
for j:=i; j<len(nums); j++ {
if nums[j]>nums[j-1] { return false }
}
break
}
if nums[i]>nums[i-1] {
for j:=i; j<len(nums); j++ {
if nums[j]<nums[j-1] { return false }
}
break
}
}
return true
}