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Count distinct substrings that contain some characters at most k times

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  • Difficulty Level : Medium
  • Last Updated : 07 Jun, 2022
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Given a integer k and a string str, the task is to count the number of distinct sub-strings such that each sub-string does not contain some specific characters more than k times. The specific characters are given as another string.
Examples: 
 

Input: str = “ababab”, anotherStr = “bcd”, k = 1 
Output:
All valid sub-strings are “a”, “b”, “ab”, “ba” and “aba”
Input: str = “acbacbacaa”, anotherStr = “ycb”, k = 2 
Output:
 

 

Approach: 
 

  • Store characters of anotherStr in a boolean array of size 256 for quick lookip
  • Traverse through all substrings of given string. For every substring, keep the count of illegal characters in anotherStr.
  • If the count of these characters exceeds the value of k then break out of the inner loop.
  • Else, store this sub-string in an hash table to keep distinct substrings.

Below is the implementation of the above approach: 
 

C++




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
const int MAX_CHAR = 256;
 
// Function to return the count of valid sub-strings
int countSubStrings(string s, string anotherStr, int k)
{
    // Store all characters of anotherStr in a
    // direct index table for quick lookup.
    bool illegal[MAX_CHAR] = { false };
    for (int i = 0; i < anotherStr.size(); i++)
        illegal[anotherStr[i]] = true;
 
    // To store distinct output substrings
    unordered_set<string> us;
 
    // Traverse through the given string and
    // one by one generate substrings beginning
    // from s[i].
    for (int i = 0; i < s.size(); ++i) {
 
        // One by one generate substrings ending
        // with s[j]
        string ss = "";
        int count = 0;
        for (int j = i; j < s.size(); ++j) {
 
            // If character is illegal
            if (illegal[s[j]])
                ++count;
            ss = ss + s[j];
 
            // If current substring is valid
            if (count <= k) {
                us.insert(ss);
            }
 
            // If current substring is invalid,
            // adding more characters would not
            // help.
            else
                break;
        }
    }
 
    // Return the count of distinct sub-strings
    return us.size();
}
 
// Driver code
int main()
{
    string str = "acbacbacaa";
    string anotherStr = "abcdefghijklmnopqrstuvwxyz";
    int k = 2;
    cout << countSubStrings(str, anotherStr, k);
    return 0;
}

Java




// Java implementation of the approach
import java.util.*;
 
class GFG {
 
    static int MAX_CHAR = 256;
 
    // Function to return the count of valid sub-strings
    static int countSubStrings(String s, String anotherStr, int k)
    {
        // Store all characters of anotherStr in a
        // direct index table for quick lookup.
        boolean illegal[] = new boolean[MAX_CHAR];
        for (int i = 0; i < anotherStr.length(); i++)
        {
            illegal[anotherStr.charAt(i)] = true;
        }
 
        // To store distinct output substrings
        HashSet<String> us = new HashSet<String>();
 
        // Traverse through the given string and
        // one by one generate substrings beginning
        // from s[i].
        for (int i = 0; i < s.length(); ++i)
        {
 
            // One by one generate substrings ending
            // with s[j]
            String ss = "";
            int count = 0;
            for (int j = i; j < s.length(); ++j)
            {
 
                // If character is illegal
                if (illegal[s.charAt(j)])
                {
                    ++count;
                }
                ss = ss + s.charAt(j);
 
                // If current substring is valid
                if (count <= k)
                {
                    us.add(ss);
                }
                 
                // If current substring is invalid,
                // adding more characters would not
                // help.
                else
                {
                    break;
                }
            }
        }
 
        // Return the count of distinct sub-strings
        return us.size();
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str = "acbacbacaa";
        String anotherStr = "abcdefghijklmnopqrstuvwxyz";
        int k = 2;
        System.out.println(countSubStrings(str, anotherStr, k));
    }
}
 
// This code is contributed by PrinciRaj1992

Python3




# Python3 implementation of the approach
 
MAX_CHAR = 256
 
# Function to return the count
# of valid sub-strings
def countSubStrings(s, anotherStr, k) :
     
    # Store all characters of anotherStr in
    # a direct index table for quick lookup.
    illegal = [False] * MAX_CHAR
     
    for i in range(len(anotherStr)) :
        illegal[ord(anotherStr[i])] = True
         
    # To store distinct output substrings
    us = set()
     
    # Traverse through the given string
    # and one by one generate substrings
    # beginning from s[i].
    for i in range(len(s)) :
         
        # One by one generate substrings
        # ending with s[j]
        ss = ""
         
        count = 0
        for j in range(i, len(s)) :
             
            # If character is illegal
            if (illegal[ord(s[j])]) :
                count += 1
            ss = ss + s[j]
             
            # If current substring is valid
            if (count <= k) :
                us.add(ss)
             
            # If current substring is invalid,
            # adding more characters would not
            # help.
            else :
                break
     
    # Return the count of distinct
    # sub-strings
    return len(us)
 
# Driver code
if __name__ == "__main__" :
 
    string = "acbacbacaa"
    anotherStr = "abcdefghijklmnopqrstuvwxyz"
    k = 2
    print(countSubStrings(string,
                          anotherStr, k))
 
# This code is contributed by Ryuga

C#




// C# implementation of the approach
using System;
using System.Collections.Generic;
 
class GFG
{
    static int MAX_CHAR = 256;
 
    // Function to return the count
    // of valid sub-strings
    static int countSubStrings(String s,
                        String anotherStr, int k)
    {
         
        // Store all characters of anotherStr in a
        // direct index table for quick lookup.
        bool []illegal = new bool[MAX_CHAR];
        for (int i = 0; i < anotherStr.Length; i++)
        {
            illegal[anotherStr[i]] = true;
        }
 
        // To store distinct output substrings
        HashSet<String> us = new HashSet<String>();
 
        // Traverse through the given
        // string and one by one generate
        // substrings beginning from s[i].
        for (int i = 0; i < s.Length; ++i)
        {
 
            // One by one generate substrings
            // ending with s[j]
            String ss = "";
            int count = 0;
            for (int j = i; j < s.Length; ++j)
            {
 
                // If character is illegal
                if (illegal[s[j]])
                {
                    ++count;
                }
                ss = ss + s[j];
 
                // If current substring is valid
                if (count <= k)
                {
                    us.Add(ss);
                }
                 
                // If current substring is invalid,
                // adding more characters would not
                // help.
                else
                {
                    break;
                }
            }
        }
 
        // Return the count of distinct sub-strings
        return us.Count;
    }
 
    // Driver code
    public static void Main()
    {
        String str = "acbacbacaa";
        String anotherStr = "abcdefghijklmnopqrstuvwxyz";
        int k = 2;
        Console.WriteLine(countSubStrings(str, anotherStr, k));
    }
}
 
//This code is contributed by 29AjayKumar

Javascript




<script>
 
// js implementation of the approach
 
let MAX_CHAR = 256;
 
// Function to return the count of valid sub-strings
function countSubStrings( s, anotherStr, k)
{
    // Store all characters of anotherStr in a
    // direct index table for quick lookup.
    let illegal = [];
    for(let i = 0;i<256;i++)
         illegal.push(false);
    for (let i = 0; i < anotherStr.length; i++)
        illegal[anotherStr[i]] = true;
 
    // To store distinct output substrings
    let us = new Set();
 
    // Traverse through the given string and
    // one by one generate substrings beginning
    // from s[i].
    for (let i = 0; i < s.length; ++i) {
 
        // One by one generate substrings ending
        // with s[j]
        let ss = "";
        let count = 0;
        for (let j = i; j < s.length; ++j) {
 
            // If character is illegal
            if (illegal[s[j]])
                ++count;
            ss = ss + s[j];
 
            // If current substring is valid
            if (count <= k) {
                us.add(ss);
            }
 
            // If current substring is invalid,
            // adding more characters would not
            // help.
            else
                break;
        }
    }
 
    // Return the count of distinct sub-strings
    return us.size;
}
 
// Driver code
let str = "acbacbacaa";
let anotherStr = "abcdefghijklmnopqrstuvwxyz";
let k = 2;
document.write(countSubStrings(str, anotherStr, k));
 
</script>

Output: 

8

 


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