[LeetCode] 896. Monotonic Array (C++)

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[LeetCode] 896. Monotonic Array (C++)

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An array is monotonic if it is either monotone increasing or monotone decreasing.

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].

Return true if and only if the given array A is monotonic.

Example 1:

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

Example 2:

Input: [6,5,4,4]
Output: true

Example 3:

Input: [1,3,2]
Output: false

Example 4:

Input: [1,2,4,5]
Output: true

Example 5:

Input: [1,1,1]
Output: true

Note:

1 <= A.length <= 50000
-100000 <= A[i] <= 100000

class Solution {
public:
    bool isMonotonic(vector<int>& A) {
        int i=0; 
        /*
        Walk Up
        Array A is monotone increasing
        */
        int j=0;
        /*
        Walk Down
        Array A is monotone decreasing
        */
        while(i+1<A.size() && A.at(i)<=A.at(i+1)) {
            i++;
        }
        while(j+1<A.size() && A.at(j)>=A.at(j+1)) {
            j++;
        }
        return (i==A.size()-1)||(j==A.size()-1);
    }
};


/*
Submission Detail:

Runtime: 84 ms, faster than 72.40% of C++ online submissions for Monotonic Array.
Memory Usage: 13.9 MB, less than 100.00% of C++ online submissions for Monotonic Array.

*/