Program to check if an array is sorted or not (Iterative and Recursive)

Given an array of size n, write a program to check if it is sorted in ascending order or not. Equal values are allowed in array and two consecutive equal values are considered sorted.

Examples:

Input : 20 21 45 89 89 90
Output : Yes

Input : 20 20 45 89 89 90
Output : Yes

Input : 20 20 78 98 99 97
Output : No

Recursive approach:

The basic idea for recursive approach:

1: If size of array is zero or one, return true.
2: Check last two elements of array, if they are
   sorted, perform a recursive call with n-1
   else, return false.
If all the elements will be found sorted, n will
eventually fall to one, satisfying Step 1.

Below is the implementation using recursion:

C++

// Recursive approach to check if an 
// Array is sorted or not 
#include <bits/stdc++.h> 
using namespace std; 
  
// Function that returns 0 if a pair 
// is found unsorted 
int arraySortedOrNot(int arr[], int n) 
{ 
    // Array has one or no element or the 
    // rest are already checked and approved. 
    if (n == 1 || n == 0) 
        return 1; 
  
    // Unsorted pair found (Equal values allowed) 
    if (arr[n - 1] < arr[n - 2]) 
        return 0; 
  
    // Last pair was sorted 
    // Keep on checking 
    return arraySortedOrNot(arr, n - 1); 
} 
  
// Driver code 
int main() 
{ 
    int arr[] = { 20, 23, 23, 45, 78, 88 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
    if (arraySortedOrNot(arr, n)) 
        cout << "Yes
"; 
    else
        cout << "No
"; 
} 

/div>

Java

// Recursive approach to check if an 
// Array is sorted or not 
  
class CkeckSorted { 
    // Function that returns 0 if a pair 
    // is found unsorted 
    static int arraySortedOrNot(int arr[], int n) 
    { 
        // Array has one or no element or the 
        // rest are already checked and approved. 
        if (n == 1 || n == 0) 
            return 1; 
  
        // Unsorted pair found (Equal values allowed) 
        if (arr[n - 1] < arr[n - 2]) 
            return 0; 
  
        // Last pair was sorted 
        // Keep on checking 
        return arraySortedOrNot(arr, n - 1); 
    } 
  
    // main function 
    public static void main(String[] args) 
    { 
        int arr[] = { 20, 23, 23, 45, 78, 88 }; 
        int n = arr.length; 
        if (arraySortedOrNot(arr, n) != 0) 
            System.out.println("Yes"); 
        else
            System.out.println("No"); 
    } 
} 

Python3

# Recursive approach to check if an 
# Array is sorted or not 
  
# Function that returns 0 if a pair 
# is found unsorted 
def arraySortedOrNot(arr): 
      
    # Calculating length 
    n = len(arr) 
      
    # Array has one or no element or the 
    # rest are already checked and approved. 
    if n == 1 or n == 0: 
        return True
          
    # Recursion applied till last element 
    return arr[0]<= arr[1] and arraySortedOrNot(arr[1:]) 
  
  
arr = [20, 23, 23, 45, 78, 88] 
  
# Displaying result 
if arraySortedOrNot(arr): print("Yes") 
else: print("No")  

Program to check if an array is sorted or not (Iterative and Recursive)

C++

Java

Python3

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