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: 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++
// C++ program for the above approach #include <bits/stdc++.h> 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); } |
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!
