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95 lines
1.6 KiB
Markdown
95 lines
1.6 KiB
Markdown
# [896. Monotonic Array](https://leetcode.com/problems/monotonic-array/)
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## 题目
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An array is *monotonic* if it is either monotone increasing or monotone decreasing.
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An array `A` is monotone increasing if for all `i <= j`, `A[i] <= A[j]`. An array `A` is monotone decreasing if for all `i <= j`, `A[i] >= A[j]`.
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Return `true` if and only if the given array `A` is monotonic.
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**Example 1**:
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```
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Input: [1,2,2,3]
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Output: true
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```
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**Example 2**:
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```
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Input: [6,5,4,4]
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Output: true
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```
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**Example 3**:
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```
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Input: [1,3,2]
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Output: false
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```
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**Example 4**:
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```
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Input: [1,2,4,5]
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Output: true
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```
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**Example 5**:
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```
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Input: [1,1,1]
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Output: true
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```
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**Note**:
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1. `1 <= A.length <= 50000`
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2. `-100000 <= A[i] <= 100000`
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## 题目大意
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如果数组是单调递增或单调递减的，那么它是单调的。如果对于所有 i <= j，A[i] <= A[j]，那么数组 A 是单调递增的。 如果对于所有 i <= j，A[i]> = A[j]，那么数组 A 是单调递减的。当给定的数组 A 是单调数组时返回 true，否则返回 false。
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## 解题思路
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- 判断给定的数组是不是单调(单调递增或者单调递减)的。
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- 简单题，按照题意循环判断即可。
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## 代码
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```go
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func isMonotonic(A []int) bool {
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if len(A) <= 1 {
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return true
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}
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if A[0] < A[1] {
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return inc(A[1:])
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}
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if A[0] > A[1] {
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return dec(A[1:])
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}
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return inc(A[1:]) || dec(A[1:])
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}
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func inc(A []int) bool {
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for i := 0; i < len(A)-1; i++ {
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if A[i] > A[i+1] {
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return false
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}
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}
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return true
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}
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func dec(A []int) bool {
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for i := 0; i < len(A)-1; i++ {
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if A[i] < A[i+1] {
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return false
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}
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}
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return true
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}
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``` |