Lexicographically next string

Difficulty Level : Easy
Last Updated : 13 May, 2021

Given a string, find lexicographically next string.
Examples:

Input : geeks
Output : geekt
The last character 's' is changed to 't'.

Input : raavz
Output : raawz
Since we can't increase last character, 
we increment previous character.

Input :  zzz
Output : zzza

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If string is empty, we return ‘a’. If string contains all characters as ‘z’, we append ‘a’ at the end. Otherwise we find first character from end which is not z and increment it.

C++

// C++ program to find lexicographically next
// string
#include <bits/stdc++.h>
using namespace std;
 
string nextWord(string s)
{
    // If string is empty.
    if (s == "")
        return "a";
 
    // Find first character from right
    // which is not z.
     
    int i = s.length() - 1;
    while (s[i] == 'z' && i >= 0)
        i--;
 
    // If all characters are 'z', append
    // an 'a' at the end.
    if (i == -1)
        s = s + 'a';
 
    // If there are some non-z characters
    else
        s[i]++;
 
    return s;
}
 
// Driver code
int main()
{
    string str = "samez";
    cout << nextWord(str);
    return 0;
}

Java

// Java program to find
// lexicographically next string
import java.util.*;
 
class GFG
{
public static String nextWord(String str)
{
     
    // if string is empty
    if (str == "")
    return "a";
     
    // Find first character from
    // right which is not z.
    int i = str.length() - 1;
    while (str.charAt(i) == 'z' && i >= 0)
        i--;
         
    // If all characters are 'z',
    // append an 'a' at the end.
    if (i == -1)
        str = str + 'a';
 
// If there are some
// non-z characters
else
    str = str.substring(0, i) +
         (char)((int)(str.charAt(i)) + 1) +
                      str.substring(i + 1);
return str;
}
 
// Driver Code
public static void main (String[] args)
{
    String str = "samez";
    System.out.print(nextWord(str));
}
}
 
// This code is contributed
// by Kirti_Mangal

Python3

# Python 3 program to find lexicographically
# next string
 
def nextWord(s):
     
    # If string is empty.
    if (s == " "):
        return "a"
 
    # Find first character from right
    # which is not z.
    i = len(s) - 1
    while (s[i] == 'z' and i >= 0):
        i -= 1
 
    # If all characters are 'z', append
    # an 'a' at the end.
    if (i == -1):
        s = s + 'a'
 
    # If there are some non-z characters
    else:
        s = s.replace(s[i], chr(ord(s[i]) + 1), 1)
 
    return s
 
# Driver code
if __name__ == '__main__':
    str = "samez"
    print(nextWord(str))
     
# This code is contributed by
# Sanjit_Prasad

C#

// C# program to find
// lexicographically next string
using System;
 
class GFG
{
public static string nextWord(string str)
{
 
    // if string is empty
    if (str == "")
    {
    return "a";
    }
 
    // Find first character from
    // right which is not z.
    int i = str.Length - 1;
    while (str[i] == 'z' && i >= 0)
    {
        i--;
    }
 
    // If all characters are 'z',
    // append an 'a' at the end.
    if (i == -1)
    {
        str = str + 'a';
    }
 
    // If there are some
    // non-z characters
    else
    {
        str = str.Substring(0, i) +
             (char)((int)(str[i]) + 1) +
              str.Substring(i + 1);
    }
    return str;
}
 
// Driver Code
public static void Main(string[] args)
{
    string str = "samez";
    Console.Write(nextWord(str));
}
}
 
// This code is contributed by Shrikant13

Javascript

<script>
 
// Javascript program to find lexicographically next
// string
 
function nextWord(s)
{
    // If string is empty.
    if (s == "")
        return "a";
 
    // Find first character from right
    // which is not z.
     
    var i = s.length - 1;
    while (s[i] == 'z' && i >= 0)
        i--;
 
    // If all characters are 'z', append
    // an 'a' at the end.
    if (i == -1)
        s = s + 'a';
 
    // If there are some non-z characters
    else
        s[i] = String.fromCharCode(s[i].charCodeAt(0)+1);
 
    return s.join('');
}
 
// Driver code
var str = "samez".split('');
document.write( nextWord(str));
 
// This code is contributed by noob2000.
</script>

Output:

samfz

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Lexicographically next string

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