Sub-strings of a string that are prefix of the same string

Given a string str, the task is to count all possible sub-strings of the given string that are prefix of the same string.

Examples:

Input: str = “ababc”
Output: 7
All possible sub-string are “a”, “ab”, “aba”, “abab”, “ababc”, “a” and “ab”

Input: str = “abdabc”
Output: 8

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Traverse the string character by character, if the current character is equal to the first character of the string then count all possible sub-strings starting from here that are also the prefixes of str and add it to count. After the complete string has been traversed, print the count.

Below is the implementation of the above approach:

C++

// C++ implementation of the approach 
#include <iostream> 
#include <string> 
using namespace std; 
  
int subStringsStartingHere(string str, int n, int index); 
  
// Function to return the count of all possible sub-strings 
// of str that are also the prefixes of str 
int countSubStrings(string str, int n) 
{ 
    int count = 0; 
    for (int i = 0; i < n; i++) 
    { 
  
        // If current character is equal to  
        // the starting character of str 
        if (str[i] == str[0]) 
            count += subStringsStartingHere(str, n, i); 
    } 
    return count; 
} 
  
// Function to return the count of sub-strings starting 
// from startIndex that are also the prefixes of str 
int subStringsStartingHere(string str, int n, 
                            int startIndex) 
{ 
    int count = 0, i = startIndex ; 
    while (i <= n) 
    { 
        if (str.substr(0,i) == str.substr(startIndex, i)) 
        { 
            count++; 
        } 
        else
            break; 
        i++; 
    } 
  
    return count; 
} 
  
  
// Driver code 
int main()  
{ 
    string str = "ababc"; 
    int n = str.length(); 
    cout << (countSubStrings(str, n)); 
} 
  
// This code is contributed by Rajput-Ji 

Java

// Java implementation of the approach 
public class GFG { 
  
    // Function to return the count of sub-strings starting 
    // from startIndex that are also the prefixes of str 
    public static int subStringsStartingHere(String str, int n, 
                                             int startIndex) 
    { 
        int count = 0, i = startIndex + 1; 
        while (i <= n) { 
            if (str.startsWith(str.substring(startIndex, i))) { 
                count++; 
            } 
            else
                break; 
            i++; 
        } 
  
        return count; 
    } 
  
    // Function to return the count of all possible sub-strings 
    // of str that are also the prefixes of str 
    public static int countSubStrings(String str, int n) 
    { 
        int count = 0; 
  
        for (int i = 0; i < n; i++) { 
  
            // If current character is equal to  
            // the starting character of str 
            if (str.charAt(i) == str.charAt(0)) 
                count += subStringsStartingHere(str, n, i); 
        } 
  
        return count; 
    } 
  
    // Driver code 
    public static void main(String[] args) 
    { 
        String str = "ababc"; 
        int n = str.length(); 
        System.out.println(countSubStrings(str, n)); 
    } 
} 

Python3

# Python3 implementation of the approach  
  
# Function to return the count of sub-strings starting  
# from startIndex that are also the prefixes of string  
def subStringsStartingHere(string, n, startIndex) : 
    count = 0
    i = startIndex + 1
      
    while(i <= n) : 
        if string.startswith(string[startIndex : i]) : 
            count += 1
        else : 
            break
          
        i += 1
      
    return count 
  
# Function to return the count of all possible sub-strings  
# of string that are also the prefixes of string  
def countSubStrings(string, n) : 
    count = 0
      
    for i in range(n) : 
          
        # If current character is equal to   
        # the starting character of str  
        if string[i] == string[0] : 
            count += subStringsStartingHere(string, n, i) 
      
    return count 
  
  
# Driver Code 
if __name__ == "__main__" : 
      
    string = "ababc"
    n = len(string) 
    print(countSubStrings(string, n)) 
  
# this code is contributed by Ryuga 

C#

// C# implementation of the approach 
using System; 
class GFG { 
   
    // Function to return the count of sub-strings starting 
    // from startIndex that are also the prefixes of str 
    static int subStringsStartingHere(String str, int n, 
                                             int startIndex) 
    { 
        int count = 0, i = startIndex + 1; 
        while (i <= n) { 
            if (str.StartsWith(str.Substring(startIndex, i-startIndex))) { 
                count++; 
            } 
            else
                break; 
            i++; 
        } 
   
        return count; 
    } 
   
    // Function to return the count of all possible sub-strings 
    // of str that are also the prefixes of str 
    static int countSubStrings(String str, int n) 
    { 
        int count = 0; 
   
        for (int i = 0; i < n; i++) { 
   
            // If current character is equal to  
            // the starting character of str 
            if (str[i] == str[0]) 
                count += subStringsStartingHere(str, n, i); 
        } 
   
        return count; 
    } 
   
    // Driver code 
    static public void Main(String []args) 
    { 
        String str = "ababc"; 
        int n = str.Length; 
        Console.WriteLine(countSubStrings(str, n)); 
    } 
} 
//contributed by Arnab Kundu 

Output:

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

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