Split a string into maximum number of unique substrings

Last Updated : 18 Jul, 2021

Given string str, the task is to split the string into the maximum number of unique substrings possible and print their count.

Examples:

Input: str = "ababccc"
Output: 5
Explanation:
Split the given string into the substrings "a", "b", "ab", "c" and "cc".
Therefore, the maximum count of unique substrings is 5.

Input: str = "aba"
Output: 2

Approach: The problem can be solved by the Greedy approach. Follow the steps below to solve the problem:

Initialize a Set S.
Iterate over the characters of the string str and for each i and find the substring up to that index.
If the given substring is not present in the Set S, insert it updates the maximum count, and remove it from the Set, because the same character cannot be reused.
Return the maximum count.

Below is the implementation of the above approach:

C++

// CPP program for the above approach
#include<bits/stdc++.h>
using namespace std;

// Utility function to find maximum count of
// unique substrings by splitting the string
int maxUnique(string S, set<string> st)
{

  // Stores maximum count of unique substring
  // by splitting the string into substrings
  int mx = 0;

  // Iterate over the characters of the string
  for (int i = 1; i <= S.length(); i++)
  {

    // Stores prefix substring
    string tmp = S.substr(0, i);

    // Check if the current substring
    // already exists
    if (st.find(tmp) == st.end()) 
    {

      // Insert tmp into set
      st.insert(tmp);

      // Recursively call for remaining
      // characters of string
      mx = max(mx, maxUnique(S.substr(i), st) + 1);

      // Remove from the set
      st.erase(tmp);
    }
  }

  // Return answer
  return mx;
}


// Function to find the maximum count of
// unique substrings by splitting a string
// into maximum number of unique substrings
int maxUniqueSplit(string S)
{
  set<string> st;
  return maxUnique(S, st);
}

// Driver Code
int main()
{
  string S = "ababccc";
  int res = maxUniqueSplit(S);

  cout<<res;
}

// This code is contributed by jana_sayantan.

Java

// Java program for the above approach
import java.io.*;
import java.util.*;
class Solution {

    // Function to find the maximum count of
    // unique substrings by splitting a string
    // into maximum number of unique substrings
    public int maxUniqueSplit(String S)
    {
        return maxUnique(S, new HashSet<String>());
    }

    // Utility function to find maximum count of
    // unique substrings by splitting the string
    public int maxUnique(String S, Set<String> set)
    {

        // Stores maximum count of unique substring
        // by splitting the string into substrings
        int max = 0;

        // Iterate over the characters of the string
        for (int i = 1; i <= S.length(); i++) {

            // Stores prefix substring
            String tmp = S.substring(0, i);

            // Check if the current substring
            // already exists
            if (!set.contains(tmp)) {

                // Insert tmp into set
                set.add(tmp);

                // Recursively call for remaining
                // characters of string
                max = Math.max(max, maxUnique(
                                        S.substring(i), set)
                                        + 1);

                // Remove from the set
                set.remove(tmp);
            }
        }

        // Return answer
        return max;
    }
}

// Driver Code
class GFG {

    public static void main(String[] args)
    {
        Solution st = new Solution();
        String S = "ababccc";
        int res = st.maxUniqueSplit(S);

        System.out.println(res);
    }
}

Python3

# Python3 program for the above approach

# Utility function to find maximum count of
# unique substrings by splitting the string
def maxUnique(S):
    global d

    # Stores maximum count of unique substring
    # by splitting the string into substrings
    maxm = 0

    # Iterate over the characters of the string
    for i in range(1, len(S) + 1):

        # Stores prefix substring
        tmp = S[0:i]

        # Check if the current substring
        # already exists
        if (tmp not in d):

            # Insert tmp into set
            d[tmp] = 1

            # Recursively call for remaining
            # characters of string
            maxm = max(maxm, maxUnique(S[i:]) + 1)

            # Remove from the set
            del d[tmp]

    # Return answer
    return maxm

# Driver Code
if __name__ == '__main__':
  
    # Solution st = new Solution()
    S = "ababccc"
    d = {}
    res = maxUnique(S)
    # d = {}

    print(res)

# This code is contributed by mohit kumar 29.

// C# program for the above approach
using System;
using System.Collections.Generic;

class GFG {

  // Function to find the maximum count of
  // unique substrings by splitting a string
  // into maximum number of unique substrings
  public int maxUniqueSplit(String S)
  {
    return maxUnique(S, new HashSet<String>());
  }

  // Utility function to find maximum count of
  // unique substrings by splitting the string
  public int maxUnique(String S, HashSet<String> set)
  {

    // Stores maximum count of unique substring
    // by splitting the string into substrings
    int max = 0;

    // Iterate over the characters of the string
    for (int i = 1; i <= S.Length; i++) {

      // Stores prefix substring
      String tmp = S.Substring(0, i);

      // Check if the current substring
      // already exists
      if (!set.Contains(tmp)) {

        // Insert tmp into set
        set.Add(tmp);

        // Recursively call for remaining
        // characters of string
        max = Math.Max(max, maxUnique(
          S.Substring(i), set)
                       + 1);

        // Remove from the set
        set.Remove(tmp);
      }
    }

    // Return answer
    return max;
  }
}

// Driver Code
public class GFG {

  public static void Main(String[] args)
  {
    Solution st = new Solution();
    String S = "ababccc";
    int res = st.maxUniqueSplit(S);

    Console.WriteLine(res);
  }
}

// This code contributed by shikhasingrajput

JavaScript

<script>

// Javascript program for the above approach

// Utility function to find maximum count of
// unique substrings by splitting the string
function maxUnique(S, st)
{

  // Stores maximum count of unique substring
  // by splitting the string into substrings
  var mx = 0;

  // Iterate over the characters of the string
  for (var i = 1; i <= S.length; i++)
  {

    // Stores prefix substring
    var tmp = S.substring(0, i);

    // Check if the current substring
    // already exists
    if (!st.has(tmp)) 
    {

      // Insert tmp into set
      st.add(tmp);

      // Recursively call for remaining
      // characters of string
      mx = Math.max(mx, maxUnique(S.substring(i), st) + 1);

      // Remove from the set
      st.delete(tmp);
    }
  }

  // Return answer
  return mx;
}


// Function to find the maximum count of
// unique substrings by splitting a string
// into maximum number of unique substrings
function maxUniqueSplit(S)
{
  var st = new Set();
  return maxUnique(S, st);
}

// Driver Code
var S = "ababccc";
var res = maxUniqueSplit(S);
document.write( res);


</script>

Output:

Time Complexity: O(2^N )

Auxiliary Space: O(N)

Split a string into maximum number of unique substrings

rohit2sahu

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