0800 - 0899
0896 - Monotonic Array (Easy)
Problem Statement
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 trueif the given array is monotonic, orfalseotherwise.
Example 1:
Input: nums = [1,2,2,3]
Output: trueExample 2:
Input: nums = [6,5,4,4]
Output: trueExample 3:
Input: nums = [1,3,2]
Output: falseConstraints:
1 <= nums.length <= 10^5-10^5 <= nums[i] <= 10^5
Approach 1: Two Loops
class Solution {
public:
bool isMonotonic(vector<int>& nums) {
int n = nums.size(), ok = 1;
// check for monotone increasing
for (int i = 1 ; i < n; i++) ok &= nums[i - 1] <= nums[i];
// if it is monotone increasing, return true
if (ok) return true;
// reset ok
ok = 1;
// check for monotone decreasing
for (int i = n - 2; i >= 0; i--) ok &= nums[i] >= nums[i + 1];
// return the answer
return ok;
}
};Approach 2: One Pass
class Solution {
public:
bool isMonotonic(vector<int>& nums) {
int n = nums.size(), inc = 1, dec = 1;
for (int i = 1 ; i < n; i++) {
// check for monotone increasing
inc &= nums[i - 1] <= nums[i];
// check for monotone decreasing
dec &= nums[i - 1] >= nums[i];
}
// the given is monotonic if either one is true
return inc || dec;
}
};