Lexicographical Maximum substring of string

Given a string s we have to find the lexicographical maximum substring of a string

Examples:

Input : s = "ababaa"
Output : babaa
Explanation : "babaa" is the maximum lexicographic susbtring formed from this string

Input : s = "asdfaa"
Output : sdfaa

The idea is simple, we traverse through all substrings. For every substring, we compare it with current result and update result if needed.



Below is the implementation:

C++

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// CPP program to find the lexicographically
// maximum substring.
#include <bits/stdc++.h>
using namespace std;
  
string LexicographicalMaxString(string str)
{
    // loop to find the max leicographic 
    // substring in the substring array
    string mx = "";
    for (int i = 0; i < str.length(); ++i)
        mx = max(mx, str.substr(i));
  
    return mx;
}
  
// Driver code
int main()
{
    string str = "ababaa";
    cout << LexicographicalMaxString(str);
    return 0;
}

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Java

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//Java program to find the lexicographically
// maximum substring.
  
class GFG {
  
    static String LexicographicalMaxString(String str) {
        // loop to find the max leicographic 
        // substring in the substring array
        String mx = "";
        for (int i = 0; i < str.length(); ++i) {
            if (mx.compareTo(str.substring(i)) <= 0) {
                mx = str.substring(i);
            }
        }
  
        return mx;
    }
  
   // Driver code
    public static void main(String[] args) {
        String str = "ababaa";
        System.out.println(LexicographicalMaxString(str));
    }
}
// This code is contributed by 29AjayKumar

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Python3

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# Python 3 program to find the
# lexicographically maximum substring.
def LexicographicalMaxString(str):
      
    # loop to find the max leicographic 
    # substring in the substring array
    mx = ""
    for i in range(len(str)):
        mx = max(mx, str[i:])
  
    return mx
  
# Driver code
if __name__ == '__main__':
    str = "ababaa"
    print(LexicographicalMaxString(str))
      
# This code is contributed by
# Sanjit_Prasad

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C#

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// C# program to find the lexicographically 
// maximum substring. 
  
using System;
public class GFG{
  
  
    static String LexicographicalMaxString(String str) { 
        // loop to find the max leicographic 
        // substring in the substring array 
        String mx = ""
        for (int i = 0; i < str.Length; ++i) { 
            if (mx.CompareTo(str.Substring(i)) <= 0) { 
                mx = str.Substring(i); 
            
        
  
        return mx; 
    
  
// Driver code 
    public static void Main() { 
        String str = "ababaa"
        Console.WriteLine(LexicographicalMaxString(str)); 
    
  
// This code is contributed by 29AjayKumar

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Output:

babaa

Time Complexity : O(n)
Space Complexity : O(n)

Optimization :
We find largest character and all its indexes. Now we simply traverse through all instances of the largest character to find lexicographically maximum substring.



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Improved By : 29AjayKumar, Sanjit_Prasad



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