Check if an array represents Inorder of Binary Search tree or not

Given an array of N element. The task is to check if it is Inorder traversal of any Binary Search Tree or not. Print “Yes” if it is Inorder traversal of any Binary Search Tree else print “No”.

Examples:

Input : arr[] = { 19, 23, 25, 30, 45 }
Output : Yes

Input : arr[] = { 19, 23, 30, 25, 45 }
Output : No

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

The idea is to use the fact that the inorder traversal of Binary Search Tree is sorted. So, just check if given array is sorted or not.

C++

// C++ program to check if a given array is sorted 
// or not. 
#include<bits/stdc++.h> 
using namespace std; 
  
// Function that returns true if array is Inorder 
// traversal of any Binary Search Tree or not. 
bool isInorder(int arr[], int n) 
{ 
    // Array has one or no element 
    if (n == 0 || n == 1) 
        return true; 
  
    for (int i = 1; i < n; i++) 
  
        // Unsorted pair found 
        if (arr[i-1] > arr[i]) 
            return false; 
  
    // No unsorted pair found 
    return true; 
} 
  
// Driver code 
int main() 
{ 
    int arr[] = { 19, 23, 25, 30, 45 }; 
    int n = sizeof(arr)/sizeof(arr[0]); 
      
    if (isInorder(arr, n)) 
        cout << "Yesn"; 
    else
        cout << "Non"; 
          
  return 0; 
} 

Java

// Java program to check if a given array is sorted  
// or not.  
  
class GFG { 
  
// Function that returns true if array is Inorder  
// traversal of any Binary Search Tree or not.  
    static boolean isInorder(int[] arr, int n) { 
        // Array has one or no element  
        if (n == 0 || n == 1) { 
            return true; 
        } 
  
        for (int i = 1; i < n; i++) // Unsorted pair found  
        { 
            if (arr[i - 1] > arr[i]) { 
                return false; 
            } 
        } 
  
        // No unsorted pair found  
        return true; 
    } 
// Drivers code  
  
    public static void main(String[] args) { 
        int arr[] = {19, 23, 25, 30, 45}; 
        int n = arr.length; 
        if (isInorder(arr, n)) { 
            System.out.println("Yes"); 
        } else { 
            System.out.println("Non"); 
        } 
    } 
} 
//This code is contributed by 29AjayKumar  

Python3

# Python 3 program to check if a given array  
# is sorted or not. 
  
# Function that returns true if array is Inorder 
# traversal of any Binary Search Tree or not. 
def isInorder(arr, n): 
      
    # Array has one or no element 
    if (n == 0 or n == 1): 
        return True
  
    for i in range(1, n, 1): 
          
        # Unsorted pair found 
        if (arr[i - 1] > arr[i]): 
            return False
  
    # No unsorted pair found 
    return True
  
# Driver code 
if __name__ == '__main__': 
    arr = [19, 23, 25, 30, 45] 
    n = len(arr) 
      
    if (isInorder(arr, n)): 
        print("Yes") 
    else: 
        print("No") 
          
# This code is contributed by 
# Sahil_Shelangia 

C#

// C# program to check if a given  
// array is sorted or not.  
using System; 
  
class GFG 
{ 
  
// Function that returns true if  
// array is Inorder traversal of  
// any Binary Search Tree or not.  
static bool isInorder(int[] arr, int n) 
{ 
    // Array has one or no element  
    if (n == 0 || n == 1)  
    { 
        return true; 
    } 
      
    // Unsorted pair found  
    for (int i = 1; i < n; i++)  
    { 
        if (arr[i - 1] > arr[i]) 
        { 
            return false; 
        } 
    } 
  
    // No unsorted pair found  
    return true; 
} 
  
// Driver code  
public static void Main()  
{ 
    int []arr = {19, 23, 25, 30, 45}; 
    int n = arr.Length; 
    if (isInorder(arr, n))  
    { 
        Console.Write("Yes"); 
    }  
    else
    { 
        Console.Write("Non"); 
    } 
} 
} 
  
// This code is contributed by Rajput-Ji 

PHP

<?php 
// PHP program to check if a given  
// array is sorted or not. 
  
// Function that returns true if array  
// is Inorder traversal of any Binary  
// Search Tree or not. 
function isInorder($arr, $n) 
{ 
    // Array has one or no element 
    if ($n == 0 || $n == 1) 
        return true; 
  
    for ($i = 1; $i < $n; $i++) 
  
        // Unsorted pair found 
        if ($arr[$i - 1] > $arr[$i]) 
            return false; 
  
    // No unsorted pair found 
    return true; 
} 
  
// Driver code 
$arr = array(19, 23, 25, 30, 45); 
$n = sizeof($arr); 
  
if (isInorder($arr, $n)) 
    echo "Yes"; 
else
    echo "No"; 
  
// This code is contributed 
// by Akanksha Rai 
?> 

Output:

Yes

This article is contributed by Anuj Chauhan. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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My Personal Notes

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

C++

Java

Python3

C#

PHP

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