Maximum length prefix such that frequency of each character is atmost number of characters with minimum frequency

Given a string S, the task is to find the prefix of string S with the maximum possible length such that frequency of each character in the prefix is at most the number of characters in S with minimum frequency.

Examples: 

Input: S = ‘aabcdaab’ 
Output: aabcd 
Explanation: 
Frequency of characters in the given string – 
{a: 4, b: 2, c: 1, d: 1} 
Minimum frequency in 1 and the count of minimum frequency is 2, 
So frequency of each character in the prefix can be at most 2.

Input: S = ‘aaabc’ 
Output: aa 
Explanation: 
Frequency of characters in the given string – 
{a: 3, b: 1, c: 1} 
Minimum frequency in 1 and the count of minimum frequency is 2, 
So frequency of each character in the prefix can be at most 2. 

Approach: 



Below is the implementation of the above approach:

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// Java implementation to find the prefix
// of the s such that occurrence of each
// character is atmost the count of minimum
// frequency in the s
import java.util.*;
import java.lang.*;
import java.io.*;
 
class GFG{
     
// Function to find the maximum
// possible prefix of the s
static void MaxPrefix(String s)
{   
     
    // Hash map to store the frequency
    // of the characters in the s
    Map<Character,
        Integer> Dict = new HashMap<>();
  
    // Iterate over the s to find
    // the occurence of each Character
    for(char i : s.toCharArray())
    {
        Dict.put(i, Dict.getOrDefault(i, 0) + 1);
    }
      
    int minfrequency = Integer.MAX_VALUE;
     
    // Minimum frequency of the Characters
    for(Integer x: Dict.values())
    {
        minfrequency = Math.min(minfrequency, x);   
    }
      
    int countminFrequency = 0;
       
    // Loop to find the count of minimum
    // frequency in the hash-map
    for(Map.Entry<Character,
                  Integer> x: Dict.entrySet())
    {
        if (x.getValue() == minfrequency)
            countminFrequency += 1;
    }
      
   Map<Character,
       Integer> mapper = new HashMap<>();
        
    int indi = 0;
       
    // Loop to find the maximum possible
    // length of the prefix in the s
    for(char i: s.toCharArray())
    {
        mapper.put(i, mapper.getOrDefault(i, 0) + 1);
         
        // Condition to check if the frequency
        // is greater than minimum possible freq
        if (mapper.get(i) > countminFrequency)
            break;
              
        indi += 1;
    }
               
    // maxprefix s and its length.
    System.out.println(s.substring(0, indi));
}
 
// Driver code
public static void main(String[] args)
{
     
    // s is initialize.
    String str = "aabcdaab";
     
    // str is passed in
    // MaxPrefix function.
    MaxPrefix(str);
}
}
 
// This code is contributed by offbeat
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# Python3 implementation to find the
# prefix of the string such that
# occurrence of each character is
# atmost the count of minimum
# frequency in the string
 
# Function to find the maximum
# possible prefix of the string
def MaxPrefix(string):
     
    # Hash map to store the frequency
    # of the characters in the string
    Dict = {}
    maxprefix = 0
     
    # Iterate over the string to find
    # the occurence of each Character
    for i in string:
        Dict[i] = Dict.get(i, 0) + 1
     
    # Minimum frequency of the Characters
    minfrequency = min(Dict.values())
    countminFrequency = 0
     
    # Loop to find the count of minimum
    # frequency in the hash-map
    for x in Dict:
        if (Dict[x] == minfrequency):
            countminFrequency += 1
     
    mapper = {}
    indi = 0
     
    # Loop to find the maximum possible
    # length of the prefix in the string   
    for i in string:
        mapper[i] = mapper.get(i, 0) + 1
         
        # Condition to check if the frequency
        # is greater than minimum possible freq
        if (mapper[i] > countminFrequency):
            break
        indi += 1
             
    # maxprefix string and its length.
    print(string[:indi])
 
# Driver code
if __name__ == '__main__':
     
    # String is initialize.
    str = 'aabcdaab'
    # str is passed in MaxPrefix function.
    MaxPrefix(str)
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// C# implementation to find the
// prefix of the s such that
// occurrence of each character is
// atmost the count of minimum
// frequency in the s
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
 
class GFG{
  
// Function to find the maximum
// possible prefix of the s
static void MaxPrefix(string s)
{   
     
    // Hash map to store the frequency
    // of the characters in the s
    Dictionary<char,
               int> Dict = new Dictionary<char,
                                          int>();
 
    // Iterate over the s to find
    // the occurence of each Character
    foreach(char i in s)
    {
        if (Dict.ContainsKey(i))
        {
            Dict[i]++;
        }
        else
        {
            Dict[i] = 1;
        }
    }
     
    int minfrequency = Int32.MaxValue;
      
    // Minimum frequency of the Characters
    foreach(int x in Dict.Values.ToList())
    {
        minfrequency = Math.Min(minfrequency, x);   
    }
     
    int countminFrequency = 0;
      
    // Loop to find the count of minimum
    // frequency in the hash-map
    foreach(char x in Dict.Keys.ToList())
    {
        if (Dict[x] == minfrequency)
            countminFrequency += 1;
    }
     
    Dictionary<char,
               int> mapper = new Dictionary<char,
                                            int>();
    int indi = 0;
      
    // Loop to find the maximum possible
    // length of the prefix in the s
    foreach(char i in s)
    {
        if (mapper.ContainsKey(i))
        {
            mapper[i]++;
        }
        else
        {
            mapper[i] = 1;
        }
          
        // Condition to check if the frequency
        // is greater than minimum possible freq
        if (mapper[i] > countminFrequency)
            break;
             
        indi += 1;
    }
              
    // maxprefix s and its length.
    Console.Write(s.Substring(0, indi));
}
 
// Driver Code
public static void Main(string[] args)
{
     
    // s is initialize.
    string str = "aabcdaab";
     
    // str is passed in
    // MaxPrefix function.
    MaxPrefix(str);
}
}
 
// This code is contributed by rutvik_56
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Output: 
aabcd












 

Performance Analysis: 




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