Sum of frequencies of characters of a string present in another string

• Difficulty Level : Medium
• Last Updated : 14 May, 2021

Given two strings S1 and S2 of lengths M and N respectively, the task is to calculate the sum of the frequencies of the characters of string S1 in the string S2.

Examples:

Input: S1 = “pPKf”, S2 = “KKKttsdppfP”
Output: 7
Explanation:
The character ‘p’ occurs twice in the string S2.
The character ‘P’ occurs once in the string S2.
The character ‘K’ occurs thrice in the string S2.
The character ‘f’ occurs once in the string S2.
Therefore, in total, characters of the string S1 occurs 7 times in the string S2.

Input: S1 = “geEksFOR”, S2 = “GeEksforgeEKS”
Output: 7

Naive Approach: The simplest approach is to iterate over each character of the string S1, count its frequency in the string S2

Time Complexity: O(N2)
Auxiliary Space: O(1)

Efficient Approach: The above approach can be optimized by using Hashing. Follow the steps below to solve the problem:

Below is the implementation of the above approach:

C++

 // C++ program for the above approach#includeusing namespace std; // Function to find sum of frequencies// of characters of S1 present in S2void countTotalFrequencies(string S1, string S2){   // Insert all characters of  // string S1 in the set  set bset;  for(auto x:S1)    bset.insert(x);  int count = 0;   // Traverse the string S2  for (auto x: S2)  {     // Check if X is present    // in bset or not    if (bset.find(x) != bset.end())       // Increment count by 1      count += 1;  }   // Finally, print the count  cout << count << endl; } // Driver Codeint main(){     // Given strings  string S1 = "geEksFOR";  string S2 = "GeEksforgeEKS";   countTotalFrequencies(S1, S2); } // This code is contributed by ipg2016107.

Java

 // Java program for the above approachimport java.util.HashSet; class GFG{ // Function to find sum of frequencies// of characters of S1 present in S2static void countTotalFrequencies(String S1, String S2){         // Insert all characters of    // string S1 in the set    HashSet bset = new HashSet();    char[] S1arr = S1.toCharArray();    char[] S2arr = S2.toCharArray();         for(char x : S1arr)        bset.add(x);             int count = 0;     // Traverse the string S2    for(char x : S2arr)    {                 // Check if X is present        // in bset or not        if (bset.contains(x))             // Increment count by 1            count += 1;    }     // Finally, print the count    System.out.print(count);} // Driver codepublic static void main(String[] args){         // Given strings    String S1 = "geEksFOR";    String S2 = "GeEksforgeEKS";     countTotalFrequencies(S1, S2);}} // This code is contributed by abhinavjain194

Python3

 # Python3 program for the above approach # Function to find sum of frequencies# of characters of S1 present in S2def countTotalFrequencies(S1, S2):     # Insert all characters of    # string S1 in the set    bset = set(S1)    count = 0     # Traverse the string S2    for x in S2:         # Check if X is present        # in bset or not        if x in bset:             # Increment count by 1            count += 1     # Finally, print the count    print(count) # Driver Code # Given stringsS1 = "geEksFOR"S2 = "GeEksforgeEKS" countTotalFrequencies(S1, S2)

C#

 // C# program for the above approachusing System;using System.Collections.Generic; class GFG {     // Function to find sum of frequencies// of characters of S1 present in S2static void countTotalFrequencies(string S1,                                  string S2){     // Insert all characters of    // string S1 in the set    HashSet bset = new HashSet();     foreach(char x in S1)        bset.Add(x);             int count = 0;     // Traverse the string S2    foreach(char x in S2)    {         // Check if X is present        // in bset or not        if (bset.Contains(x))             // Increment count by 1            count += 1;    }         // Finally, print the count    Console.Write(count);} // Driver codestatic void Main(){         // Given strings    string S1 = "geEksFOR";    string S2 = "GeEksforgeEKS";     countTotalFrequencies(S1, S2);}} // This code is contributed by abhinavjain194

Javascript


Output:
7

Time Complexity: O(N)
Auxiliary Space: O(N)

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