前言
本文记录LeetCode - 896. 单调数组（Monotonic Array）问题。
问题描述
判断给定数组是否为单调数组（Monotonic Array），单调递增（Monotone Increasing）或单调递减（Monotone Decreasing）。
单调递增数组：对于任意
i <= j，均有A[i] <= A[j]。单调递减数组：对于任意
i <= j，均有A[i] >= A[j]。
相关限定条件如下：
1 <= A.length <= 50000-100000 <= A[i] <= 100000
输入整型数组，判断其是否为单调数组，返回布尔值。
具体样例如下：
Input: [1, 2, 3]
Output: true
注：样例 1
Input: [1, 2, 2, 4]
Output: true
注：样例 2
Input: [1, 3, 2]
Output: false
注：样例 3
问题解答
该问题的解法简单直接，遍历数组，对比数组前后元素的数值，判断数组是否单调。共有3种情况：非单调，单调递增，单调递减。
bool isMonotonic(int* A, int ASize) {
/* Set origin status to `true`
in order to operate `&=` */
bool isIncreasing = true,
isDecreasing = true;
for (int i = 1; i < ASize; ++i) {
isIncreasing &= A[i - 1] <= A[i],
isDecreasing &= A[i - 1] >= A[i];
}
/* Only three options */
return isIncreasing || isDecreasing;
}
代码清单：
C实现
class Solution {
public:
bool isMonotonic(vector<int> A) {
/* Set origin status to `true`
in order to operate `&=` */
bool isIncreasing = true,
isDecreasing = true;
for (int i = 1; i < A.size(); ++i) {
isIncreasing &= A[i - 1] <= A[i],
isDecreasing &= A[i - 1] >= A[i];
}
/* Only three options */
return isIncreasing || isDecreasing;
}
};
代码清单：
C++实现
class Solution {
public boolean isMonotonic(int[] A) {
/* Set origin status to `true`
in order to operate `&=` */
boolean isIncreasing = true,
isDecreasing = true;
for (int i = 1; i < A.length; ++i) {
isIncreasing &= A[i - 1] <= A[i],
isDecreasing &= A[i - 1] >= A[i];
}
/* Only three options */
return isIncreasinginc || isDecreasing;
}
}
代码清单：
Java实现
class Solution:
def isMonotonic(self, A: List[int]) -> bool:
isIncreasing: bool = True
isDecreasing: bool = True
for i in range(1, len(A)):
isIncreasing &= A[i - 1] <= A[i]
isDecreasing &= A[i - 1] >= A[i]
return isIncreasing or isDecreasing
代码清单：
Python实现