Length of the smallest substring consisting of maximum distinct characters (original) (raw)

Last Updated : 5 Aug, 2024

Given a string of length N, find the length of the smallest sub-string consisting of maximum distinct characters. Note : Our output can have same character.

**Examples:

Input : "AABBBCBB"
Output : 5

Input : "AABBBCBBAC"
Output : 3
Explanation : Sub-string -> "BAC"

Input : "GEEKSGEEKSFOR"
Output : 8
Explanation : Sub-string -> "GEEKSFOR"

**Method 1 (Brute Force)

We can consider all sub-strings one by one and check for each sub-string both conditions together

1. sub-string's distinct characters is equal to maximum distinct characters
2. sub-string's length should be minimum.

**Implementation:

C++ `

/* C++ program to find the length of the smallest substring consisting of maximum distinct characters */ #include <bits/stdc++.h> using namespace std;

#define NO_OF_CHARS 256

// Find maximum distinct characters in any string int max_distinct_char(string str, int n){

// Initialize all character's count with 0
int count[NO_OF_CHARS] = {0};

// Increase the count in array if a character
// is found
for (int i = 0; i < n;  i++)
    count[str[i]]++;

int max_distinct = 0;
for (int i = 0; i < NO_OF_CHARS;  i++)
    if (count[i] != 0)      
        max_distinct++;     

return max_distinct;

}

int smallesteSubstr_maxDistictChar(string str){

int n = str.size();     // size of given string

// Find maximum distinct characters in any string
int max_distinct = max_distinct_char(str, n);
int minl = n;   // result

// Brute force approach to find all substrings
for (int i=0 ;i<n ;i++){
    for (int j=0; j<n; j++){
        string subs =  str.substr(i,j);
        int subs_lenght = subs.size();
        int sub_distinct_char = max_distinct_char(subs, subs_lenght); 
        
        // We have to check here both conditions together
        // 1. substring's distinct characters is equal
        //    to maximum distinct characters
        // 2. substring's length should be minimum 
        if (subs_lenght < minl && max_distinct == sub_distinct_char){
            minl = subs_lenght;
        }
    }
}
return minl;

}

/* Driver program to test above function */ int main() { // Input String string str = "AABBBCBB";

int len =  smallesteSubstr_maxDistictChar(str);
cout << " The length of the smallest substring"
        " consisting of maximum distinct "
        "characters : " << len;
return 0;

}

Java

/* Java program to find the length of the smallest substring consisting of maximum distinct characters */ class GFG {

final static int NO_OF_CHARS = 256;

// Find maximum distinct characters in any string static int max_distinct_char(String str, int n) {

    // Initialize all character's count with 0
    int count[] = new int[NO_OF_CHARS];

    // Increase the count in array if a character
    // is found
    for (int i = 0; i < n; i++) {
        count[str.charAt(i)]++;
    }

    int max_distinct = 0;
    for (int i = 0; i < NO_OF_CHARS; i++) {
        if (count[i] != 0) {
            max_distinct++;
        }
    }

    return max_distinct;
}

static int smallesteSubstr_maxDistictChar(String str) {

    int n = str.length();     // size of given string

    // Find maximum distinct characters in any string
    int max_distinct = max_distinct_char(str, n);
    int minl = n;   // result

    // Brute force approach to find all substrings
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            
            String subs = null;
            if(i<j)
                subs = str.substring(i, j);
            else
                subs = str.substring(j, i);
            int subs_lenght = subs.length();
            int sub_distinct_char = max_distinct_char(subs, subs_lenght);

            // We have to check here both conditions together
            // 1. substring's distinct characters is equal
            //    to maximum distinct characters
            // 2. substring's length should be minimum 
            if (subs_lenght < minl && max_distinct == sub_distinct_char) {
                minl = subs_lenght;
            }
        }
    }
    return minl;
}

/* Driver program to test above function */
static public void main(String[] args) {
    // Input String
    String str = "AABBBCBB";

    int len = smallesteSubstr_maxDistictChar(str);
    System.out.println(" The length of the smallest substring"
            + " consisting of maximum distinct "
            + "characters : "+len);
}

}

// This code is contributed by 29AjayKumar

Python

Python 3 program to find the length

of the smallest substring consisting

of maximum distinct characters

NO_OF_CHARS = 256

Find maximum distinct characters

in any string

def max_distinct_char(str, n):

# Initialize all character's
# count with 0
count = [0] * NO_OF_CHARS

# Increase the count in array 
# if a character is found
for i in range(n):
    count[ord(str[i])] += 1

max_distinct = 0
for i in range(NO_OF_CHARS):
    if (count[i] != 0):
        max_distinct += 1    

return max_distinct

def smallesteSubstr_maxDistictChar(str):

n = len(str)     # size of given string

# Find maximum distinct characters
# in any string
max_distinct = max_distinct_char(str, n)
minl = n     # result

# Brute force approach to
# find all substrings
for i in range(n):
    for j in range(n):
        subs = str[i:j]
        subs_lenght = len(subs)
        sub_distinct_char = max_distinct_char(subs, 
                                              subs_lenght)
        
        # We have to check here both conditions together
        # 1. substring's distinct characters is equal
        # to maximum distinct characters
        # 2. substring's length should be minimum 
        if (subs_lenght < minl and 
            max_distinct == sub_distinct_char):
            minl = subs_lenght

return minl

Driver Code

if name == "main":

# Input String
str = "AABBBCBB"

l = smallesteSubstr_maxDistictChar(str);
print( "The length of the smallest substring",
       "consisting of maximum distinct",
       "characters :", l)

This code is contributed by ChitraNayal

C#

/* C# program to find the length of the smallest substring consisting of maximum distinct characters */ using System;

class GFG {

static int NO_OF_CHARS = 256;

// Find maximum distinct characters in any string
static int max_distinct_char(String str, int n) 
{

    // Initialize all character's count with 0
    int []count = new int[NO_OF_CHARS];

    // Increase the count in array if a character
    // is found
    for (int i = 0; i < n; i++) 
    {
        count[str[i]]++;
    }

    int max_distinct = 0;
    for (int i = 0; i < NO_OF_CHARS; i++)
    {
        if (count[i] != 0) 
        {
            max_distinct++;
        }
    }

    return max_distinct;
}

static int smallesteSubstr_maxDistictChar(String str)
{

    int n = str.Length;     // size of given string

    // Find maximum distinct characters in any string
    int max_distinct = max_distinct_char(str, n);
    int minl = n; // result

    // Brute force approach to find all substrings
    for (int i = 0; i < n; i++) 
    {
        for (int j = 0; j < n; j++) 
        {
            
            String subs = null;
            if(i < j)
                subs = str.Substring(i, str.Length-j);
            else
                subs = str.Substring(j, str.Length-i);
            int subs_lenght = subs.Length;
            int sub_distinct_char = max_distinct_char(subs, subs_lenght);

            // We have to check here both conditions together
            // 1. substring's distinct characters is equal
            // to maximum distinct characters
            // 2. substring's length should be minimum 
            if (subs_lenght < minl && max_distinct == sub_distinct_char)
            {
                minl = subs_lenght;
            }
        }
    }
    return minl;
}

/* Driver program to test above function */
static public void Main(String[] args)
{
    // Input String
    String str = "AABBBCBB";

    int len = smallesteSubstr_maxDistictChar(str);
    Console.WriteLine(" The length of the smallest substring"
            + " consisting of maximum distinct "
            + "characters : "+len);
}

}

// This code contributed by Rajput-Ji

JavaScript

PHP

`

Output

The length of the smallest substring consisting of maximum distinct characters : 5

**Time Complexity : **O(n 3 )
**Auxiliary Space: O(n)

**Method 2 (Efficient)

1. Count all distinct characters in given string.
2. Maintain a window of characters. Whenever the window contains all characters of given string, we shrink the window from left side to remove extra characters and then compare its length with smallest window found so far.

**Implementation:

C++ `

/* C++ program to find the length of the smallest substring consisting of maximum distinct characters */ #include <bits/stdc++.h> using namespace std;

// A function which accepts a string and returns length of // the smallest substring consisting of maximum distinct // characters int smallesteSubstr_maxDistictChar(string str) { // to get the number of unique characters unordered_set st; // traverse the string once and store the characters for (int i = 0; i < str.length(); i++) st.insert(str[i]); // number of unique characters int unique = st.size(); unordered_map<char, int> mp; // to store the result int res = INT_MAX; int j = 0; // starting index of window for (int i = 0; i < str.length(); i++) { // add the current character in window mp[str[i]]++; // while number of distinct elements in the map is // equal to unique characters and starting element // of the window has frequency more than one we keep // reducing its frequency and increasing the // starting point of the window while (mp.size() == unique && mp[str[j]] > 1) { mp[str[j]]--; j++; } // if size of map is equal to unique elements update // the result if (mp.size() == unique) res = min(i - j + 1, res); } return res; }

/* Driver program to test above function */ int main() { // Input String string str = "AABBBCBB";

int len = smallesteSubstr_maxDistictChar(str);
cout << " The length of the smallest substring"
        " consisting of maximum distinct "
        "characters : "
     << len;
return 0;

}

// This code was contributed by Abhijeet Kumar(abhijeet19403)

Java

/* Java program to find the length of the smallest substring consisting of maximum distinct characters / import java.util.;

class GFG {

static final int MAX_CHARS = 256;
// Find maximum distinct characters in any string
static int max_distinct_char(String str, int n)
{
    // Initialize all character's count with 0
    int count[] = new int[MAX_CHARS];
    int max_distinct = 0;
    // Increase the count of max_distinct if a character
    // is found to have a frequency of 1
    for (int i = 0; i < n; i++) {
        count[str.charAt(i)]++;
        if (count[str.charAt(i)] == 1)
            max_distinct++;
    }
    return max_distinct;
}
// A function which accepts a string and returns length
// of the smallest substring consisting of maximum distinct
// characters
static int smallestSubstr_maxDistictChar(String str)
{
    int n = str.length();
    // number of unique characters
    int unique = max_distinct_char(str, n);
    // to store the result
      int res = Integer.MAX_VALUE;
    Map<Character, Integer> mp
        = new HashMap<Character, Integer>();
    
    int j = 0; // starting index of window
    for (int i = 0; i < str.length(); i++) {
        // add the current character in window
        char c = str.charAt(i);
        if (mp.containsKey(c))
            mp.put(c, mp.get(c) + 1);
        else
            mp.put(c, 1);
        // while no. of distinct elements in the map is
        // equal to unique characters and starting
        // element of the window has frequency more than
        // one we keep reducing its frequency and
        // increasing the starting point of the window
      
        while (mp.size() == unique
               && mp.get(str.charAt(j)) > 1) {
            mp.put(str.charAt(j),
                   (mp.get(str.charAt(j)) - 1));
            j++;
        }
        // if size of map is equal to unique elements
        // update the result
        if (mp.size() == unique)
            res = Math.min(i - j + 1, res);
    }
    return res;
}

/* Driver program to test above function */
static public void main(String[] args)
{
    // Input String
    String str = "AABBBCBB";

    int len = smallestSubstr_maxDistictChar(str);
    System.out.println(
        " The length of the smallest substring"
        + " consisting of maximum distinct "
        + "characters : " + len);
}

}

// This code is contributed by Abhijeet Kumar(abhijeet19403)

Python

import sys import math

class GFG : MAX_CHARS = 256

# Find maximum distinct characters in any string
@staticmethod
def  max_distinct_char( str,  n) :
    # Initialize all character's count with 0
    count = [0] * (GFG.MAX_CHARS)
    max_distinct = 0
    
    # Increase the count of max_distinct if a character
    # is found to have a frequency of 1
    i = 0
    while (i < n) :
        count[ord(str[i])] += 1
        if (count[ord(str[i])] == 1) :
            max_distinct += 1
        i += 1
    return max_distinct
  
# A function which accepts a string and returns length
# of the smallest substring consisting of maximum distinct
# characters
@staticmethod
def  smallestSubstr_maxDistictChar( str) :
    n = len(str)
    
    # number of unique characters
    unique = GFG.max_distinct_char(str, n)
    
    # to store the result
    res = sys.maxsize
    mp =  dict()
    j = 0
    
    # starting index of window
    i = 0
    while (i < len(str)) :
        # add the current character in window
        c = str[i]
        if ((c in mp.keys())) :
            mp[c] = mp.get(c) + 1
        else :
            mp[c] = 1
            
        # while no. of distinct elements in the map is
        # equal to unique characters and starting
        # element of the window has frequency more than
        # one we keep reducing its frequency and
        # increasing the starting point of the window
        while (len(mp) == unique and mp.get(str[j]) > 1) :
            mp[str[j]] = (mp.get(str[j]) - 1)
            j += 1
            
        # if size of map is equal to unique elements
        # update the result
        if (len(mp) == unique) :
            res = min(i - j + 1,res)
        i += 1
    return res
  
# Driver program to test above function
@staticmethod
def main( args) :
  
    # Input String
    st = "AABBBCBB"
    len = str(GFG.smallestSubstr_maxDistictChar(st))
    print(" The length of the smallest substring" + " consisting of maximum distinct " + "characters : " + len)

if name=="main": GFG.main([])

# This code is contributed by adityaburujwale.

C#

/* C# program to find the length of the smallest substring consisting of maximum distinct characters */ using System; using System.Collections.Generic;

class GFG { static int MAX_CHARS = 256;

// Find maximum distinct characters in any string
static int max_distinct_char(String str, int n) 
{
      // Initialize all character's count with 0
    int[] count = new int[MAX_CHARS];
    int max_distinct = 0;
    // Increase the count of max_distinct if a character
    // is found to have a frequency of 1
    for (int i = 0; i < n; i++) {
        count[str[i]]++;
        if (count[str[i]] == 1)
            max_distinct++;
    }
    return max_distinct;
}

static int smallestSubstr_maxDistictChar(String str)
{
    int n = str.Length;
    // number of unique characters
    int unique = max_distinct_char(str, n);
    // to store the result
      int res = int.MaxValue;
  
    Dictionary<char, int> mp  = new Dictionary<char, int>();
    int j = 0; // starting index of window
  
    for (int i = 0; i < n; i++) {
        // add the current character in window
        if (mp.ContainsKey(str[i]))
            mp[str[i]]++;
        else
            mp.Add(str[i], 1);
        
        // while no. of distinct elements in the map is
        // equal to unique characters and starting
        // element of the window has frequency more than
        // one we keep reducing its frequency and
        // increasing the starting point of the window
        while (mp.Count == unique && mp[str[j]] > 1) 
        {
            mp[str[j]]--;
            j++;
        }
        // if size of map is equal to unique elements
        // update the result
        if (mp.Count == unique)
            res = Math.Min(i - j + 1, res);
    }
    return res;
  
}

/* Driver program to test above function */
static public void Main(String[] args)
{
    // Input String
    String str = "AABBBCBB";

    int len = smallestSubstr_maxDistictChar(str);
    Console.WriteLine(" The length of the smallest substring"
            + " consisting of maximum distinct "
            + "characters : "+len);
}

}

// This code contributed by Abhijeet Kumar(abhijeet19403)

JavaScript

 var MAX_CHARS = 256;
 
// Find maximum distinct characters in any string
function max_distinct_char(str, n)
{

    // Initialize all character's count with 0
    var count = Array(MAX_CHARS).fill(0);
    var max_distinct = 0;
    
    // Increase the count of max_distinct if a character
    // is found to have a frequency of 1
    var i=0;
    for (i; i < n; i++)
    {
        count[str.charAt(i).charCodeAt(0)]++;
        if (count[str.charAt(i).charCodeAt(0)] == 1)
        {
            max_distinct++;
        }
    }
    return max_distinct;
}

// A function which accepts a string and returns length
// of the smallest substring consisting of maximum distinct
// characters
function smallestSubstr_maxDistictChar(str)
{
    var n = str.length;
    
    // number of unique characters
    var unique = max_distinct_char(str, n);
    
    // to store the result
    var res = Number.MAX_VALUE;
    var mp = new Map();
    var j = 0;
    
    // starting index of window
    var i=0;
    for (i; i < str.length; i++)
    {
    
        // add the current character in window
        var c = str.charAt(i);
        if (mp.has(c))
        {
            mp.set(c,mp.get(c) + 1);
        }
        else 
        {
            mp.set(c,1);
        }
        
        // while no. of distinct elements in the map is
        // equal to unique characters and starting
        // element of the window has frequency more than
        // one we keep reducing its frequency and
        // increasing the starting point of the window
        while (mp.size == unique && mp.get(str.charAt(j)) > 1)
        {
            mp.set(str.charAt(j),(mp.get(str.charAt(j)) - 1));
            j++;
        }
        
        // if size of map is equal to unique elements
        // update the result
        if (mp.size == unique)
        {
            res = Math.min(i - j + 1,res);
        }
    }
    return res;
}

// Driver program to test above function

    // Input String
    var str = "AABBBCBB";
    var len = smallestSubstr_maxDistictChar(str);
    console.log(" The length of the smallest substring" + " consisting of maximum distinct " + "characters : " + len);

// This code is contributed by sourabhdalal0001.

`

Output

The length of the smallest substring consisting of maximum distinct characters : 5

**Time Complexity: O(n), As we doing linear operations on string.
**Auxiliary Space: O(n), As constant extra space is used. The size of set and map can only go upto a maximum size of 256 which is a constant thus the extra space used is also constant.

Please refer Smallest window that contains all characters of string itself more details.
**Asked In : DailyHunt