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Check if the characters of a given string are in alphabetical order
  • Difficulty Level : Basic
  • Last Updated : 13 May, 2021

Given a string ‘s’, the task is to find if the characters of the string are in alphabetical order. The string contains only lowercase characters. 
 

Examples: 

Input: Str = "aabbbcc"
Output: In alphabetical order

Input: Str = "aabbbcca"
Output: Not in alphabetical order

A simple approach: 

  • Store the string to a character array and sort the array.
  • If the characters in the sorted array are in the same order as the string then print ‘In alphabetical order ‘.
  • Print ‘Not in alphabetical order’ otherwise.

Below is the implementation of the above approach :  

C++




// C++ implementation of above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function that checks whether
// the string is in alphabetical
// order or not
bool isAlphabaticOrder(string s)
{
    // length of the string
    int n = s.length();
 
    // create a character array
    // of the length of the string
    char c[n];
 
    // assign the string
    // to character array
    for (int i = 0; i < n; i++) {
        c[i] = s[i];
    }
 
    // sort the character array
    sort(c, c + n);
 
    // check if the character array
    // is equal to the string or not
    for (int i = 0; i < n; i++)
        if (c[i] != s[i])
            return false;
         
    return true;   
}
 
// Driver code
int main()
{
    string s = "aabbbcc";
 
    // check whether the string is
    // in alphabetical order or not
    if (isAlphabaticOrder(s))
       cout << "Yes";
    else
       cout << "No";
 
    return 0;
}

Java




// Java implementation of above approach
 
// import  Arrays class
import java.util.Arrays;
 
public class GFG {
 
    // Function that checks whether
    // the string is in alphabetical
    // order or not
    static boolean isAlphabaticOrder(String s)
    {
        // length of the string
        int n = s.length();
       
        // create a character array
        // of the length of the string
        char c[] = new char [n];
       
        // assign the string
        // to character array
        for (int i = 0; i < n; i++) {
            c[i] = s.charAt(i);
        }
       
        // sort the character array
        Arrays.sort(c);
       
        // check if the character array
        // is equal to the string or not
        for (int i = 0; i < n; i++)
            if (c[i] != s.charAt(i)) 
                return false;
               
        return true;    
    }
     
    public static void main(String args[])
    {
        String s = "aabbbcc";
         
        // check whether the string is
        // in alphabetical order or not
        if (isAlphabaticOrder(s))
           System.out.println("Yes");
        else
            System.out.println("No");
           
    }
    // This Code is contributed by ANKITRAI1
}

Python3




# Python 3 implementation of above approach
 
# Function that checks whether
# the string is in alphabetical
# order or not
def isAlphabaticOrder(s):
     
    # length of the string
    n = len(s)
 
    # create a character array
    # of the length of the string
    c = [s[i] for i in range(len(s))]
 
    # sort the character array
    c.sort(reverse = False)
 
    # check if the character array
    # is equal to the string or not
    for i in range(n):
        if (c[i] != s[i]):
            return False
         
    return True
 
# Driver code
if __name__ == '__main__':
    s = "aabbbcc"
 
    # check whether the string is
    # in alphabetical order or not
    if (isAlphabaticOrder(s)):
        print("Yes")
    else:
        print("No")
 
# This code is contributed by
# Surendra_Gangwar

C#




// C# implementation of above approach
// import Arrays class
 
using System;
 
public class GFG{
     
    // Function that checks whether
    // the string is in alphabetical
    // order or not
    static bool isAlphabaticOrder(String s)
    {
        // length of the string
        int n = s.Length;
     
        // create a character array
        // of the length of the string
        char []c = new char [n];
     
        // assign the string
        // to character array
        for (int i = 0; i < n; i++) {
            c[i] = s[i];
        }
     
        // sort the character array
        Array.Sort(c);
     
        // check if the character array
        // is equal to the string or not
        for (int i = 0; i < n; i++)
            if (c[i] != s[i])
                return false;
             
        return true;    
    }
     
    static public void Main (){
        String s = "aabbbcc";
         
        // check whether the string is
        // in alphabetical order or not
        if (isAlphabaticOrder(s))
        Console.WriteLine("Yes");
        else
            Console.WriteLine("No");
         
    }
}

PHP




<?php
// PHP implementation of above approach
 
// Function that checks whether
// the string is in alphabetical
// order or not
Function isAlphabaticOrder($s)
{
     
    // length of the string
    $n = strlen($s);
 
    $c = array();
     
    // assign the string
    // to character array
    for ($i = 0; $i < $n; $i++)
    {
        $c[$i] = $s[$i];
    }
 
    // sort the character array
    sort($c);
 
    // check if the character array
    // is equal to the string or not
    for ($i = 0; $i < $n; $i++)
        if ($c[$i] != $s[$i])
            return false;
         
    return true;
}
 
// Driver code
$s = "aabbbcc";
 
// check whether the string is
// in alphabetical order or not
if (isAlphabaticOrder($s))
    echo "Yes";
else
    echo "No";
     
// This Code is contributed
// by Shivi_Aggarwal
?>

Javascript




<script>
//Javascript implementation of above approach
 
// Function that checks whether
// the string is in alphabetical
// order or not
function isAlphabaticOrder(s)
{
    // length of the string
    var n = s.length;
 
    // create a character array
    // of the length of the string
    var c = new Array(n);
 
    // assign the string
    // to character array
    for (var i = 0; i < n; i++) {
        c[i] = s[i];
    }
 
    // sort the character array
    c.sort();
 
    // check if the character array
    // is equal to the string or not
    for (var i = 0; i < n; i++)
        if (c[i] != s[i])
            return false;
         
    return true;   
}
 
s = "aabbbcc";
 
// check whether the string is
// in alphabetical order or not
if (isAlphabaticOrder(s))
  document.write( "Yes");
else
  document.write( "No");
 
//This code is contributed by SoumikMondal
</script>
Output: 



Yes

 

Time Complexity: O(N*log(N))

Auxiliary Space: O(N)
Efficient approach: 

  • Run a loop from 1 to (n-1) (where n is the length of the string)
  • Check whether the element at index ‘i’ is less than the element at index ‘i-1’.
  • If yes, then print ‘In alphabetical order ‘.
  • Print ‘Not in alphabetical order’ otherwise.

Below is the implementation of the above approach 

C++




// C++ implementation of above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function that checks whether
// the string is in alphabetical
// order or not
bool isAlphabaticOrder(string s)
{
    int n = s.length();
 
    for (int i = 1; i < n; i++) {
 
        // if element at index 'i' is less
        // than the element at index 'i-1'
        // then the string is not sorted
        if (s[i] < s[i - 1])
           return false;
    }
 
    return true;
}
 
// Driver code
int main()
{
    string s = "aabbbcc";
 
    // check whether the string is
    // in alphabetical order or not
    if (isAlphabaticOrder(s))
       cout << "Yes";
    else
       cout << "No";
 
    return 0;
}

Java




// Java implementation of above approach
public class GFG {
 
// Function that checks whether
// the string is in alphabetical
// order or not
    static boolean isAlphabaticOrder(String s) {
        int n = s.length();
 
        for (int i = 1; i < n; i++) {
 
            // if element at index 'i' is less
            // than the element at index 'i-1'
            // then the string is not sorted
            if (s.charAt(i) < s.charAt(i - 1)) {
                return false;
            }
        }
 
        return true;
    }
 
// Driver code
    static public void main(String[] args) {
        String s = "aabbbcc";
        // check whether the string is
        // in alphabetical order or not
        if (isAlphabaticOrder(s)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
    }
}
//This code is contributed by PrinciRaj1992

Python 3




# Python 3 implementation of above approach
 
# Function that checks whether
# the string is in alphabetical
# order or not
def isAlphabaticOrder(s):
 
    n = len(s)
 
    for i in range(1, n):
 
        # if element at index 'i' is less
        # than the element at index 'i-1'
        # then the string is not sorted
        if (s[i] < s[i - 1]) :
            return False
 
    return True
 
# Driver code
if __name__ == "__main__":
 
    s = "aabbbcc"
 
    # check whether the string is
    # in alphabetical order or not
    if (isAlphabaticOrder(s)):
        print("Yes")
    else:
        print("No")

C#




// C# implementation of above approach
using System;
 
public class GFG{
     
// Function that checks whether
// the string is in alphabetical
// order or not
static bool isAlphabaticOrder(string s)
{
    int n = s.Length;
 
    for (int i = 1; i < n; i++) {
 
        // if element at index 'i' is less
        // than the element at index 'i-1'
        // then the string is not sorted
        if (s[i] < s[i - 1])
        return false;
    }
 
    return true;
}
 
// Driver code
    static public void Main (){
    string s = "aabbbcc";
    // check whether the string is
    // in alphabetical order or not
    if (isAlphabaticOrder(s))
    Console.WriteLine ("Yes");
        else
    Console.WriteLine  ("No");
    }
}

PHP




<?php
// PHP implementation of above approach
 
// Function that checks whether
// the string is in alphabetical
// order or not
function isAlphabaticOrder($s)
{
    $n = strlen($s);
    for ($i = 1; $i < $n; $i++)
    {
 
        // if element at index 'i' is less
        // than the element at index 'i-1'
        // then the string is not sorted
        if ($s[$i] < $s[$i - 1])
        return false;
    }
 
    return true;
}
 
// Driver code
$s = "aabbbcc";
 
// check whether the string is
// in alphabetical order or not
if (isAlphabaticOrder($s))
    echo "Yes";
else
    echo "No";
 
// This code is contributed
// by Sach_Code
?>

Javascript




<script>
// JavaScript implementation of above approach
 
// Function that checks whether
// the string is in alphabetical
// order or not
function isAlphabaticOrder( s){
    let n = s.length;
 
    for (let i = 1; i < n; i++) {
        // if element at index 'i' is less
        // than the element at index 'i-1'
        // then the string is not sorted
        if (s[i] < s[i - 1])
           return false;
    }
    return true;
}
 
// Driver code
let s = "aabbbcc";
// check whether the string is
// in alphabetical order or not
if (isAlphabaticOrder(s))
    document.write("Yes");
else
    document.write("No");
</script>
Output: 
Yes

 

Time Complexity: O(N)
Auxiliary Space: O(1)

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