# C++ Program to Modify given array to a non-decreasing array by rotation

Given an array arr[] of size N (consisting of duplicates), the task is to check if the given array can be converted to a non-decreasing array by rotating it. If it’s not possible to do so, then print “No“. Otherwise, print “Yes“.

Examples:

Input: arr[] = {3, 4, 5, 1, 2}
Output: Yes
Explanation:Â After 2 right rotations, the array arr[] modifies to {1, 2, 3, 4, 5}

Input: arr[] = {1, 2, 4, 3}
Output: No

Approach: The idea is based on the fact that a maximum of N distinct arrays can be obtained by rotating the given array and check for each individual rotated array, whether it is non-decreasing or not. Follow the steps below to solve the problem:

• Initialize a vector, say v, and copy all the elements of the original array into it.
• Sort the vector v.
• Traverse the original array and perform the following steps:
• Rotate by 1 in each iteration.
• If the array becomes equal to vector v, print “Yes“. Otherwise, print “No“.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach `` ` `#include ``using` `namespace` `std; `` ` `// Function to check if a ``// non-decreasing array can be obtained ``// by rotating the original array ``void` `rotateArray(vector<``int``>& arr, ``int` `N) ``{ ``    ``// Stores copy of original array ``    ``vector<``int``> v = arr; `` ` `    ``// Sort the given vector ``    ``sort(v.begin(), v.end()); `` ` `    ``// Traverse the array ``    ``for` `(``int` `i = 1; i <= N; ++i) { `` ` `        ``// Rotate the array by 1 ``        ``rotate(arr.begin(), ``               ``arr.begin() + 1, arr.end()); `` ` `        ``// If array is sorted ``        ``if` `(arr == v) { `` ` `            ``cout << ``"YES"` `<< endl; ``            ``return``; ``        ``} ``    ``} `` ` `    ``// If it is not possible to ``    ``// sort the array ``    ``cout << ``"NO"` `<< endl; ``} `` ` `// Driver Code ``int` `main() ``{ ``    ``// Given array ``    ``vector<``int``> arr = { 3, 4, 5, 1, 2 }; `` ` `    ``// Size of the array ``    ``int` `N = arr.size(); `` ` `    ``// Function call to check if it is possible ``    ``// to make array non-decreasing by rotating ``    ``rotateArray(arr, N); ``}`

Output
```YES
```

Time Complexity: O(N2)
Auxiliary Space: O(N)

Please refer complete article on Modify given array to a non-decreasing array by rotation for more details!

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