Method 1:Naive Approach

Approach:

The approach used in this code is to iterate over all possible starting positions of a substring of length N in the given string str, and count the number of valid substrings. We can check if a substring is valid by using the substr function to extract a substring of length N starting from the current position, and checking if its length is equal to N.

Implementation:

C++

#include <bits/stdc++.h>
using namespace std;
 
int count_substrings(string str, int n) {
    int count = 0;
    for (int i = 0; i <= str.length() - n; i++) {
        string substring = str.substr(i, n);
        // check if the current substring has length n
        if (substring.length() == n) {
            count++;
        }
    }
    return count;
}
 
int main() {
    string str = "w3wiki";
    int n = 5;
    cout << count_substrings(str, n) << endl;
    return 0;
}

Java

public class CountSubstrings {
    public static int countSubstrings(String str, int n) {
        int count = 0;
        for (int i = 0; i <= str.length() - n; i++) {
            String substring = str.substring(i, i + n);
            // check if the current substring has length n
            if (substring.length() == n) {
                count++;
            }
        }
        return count;
    }
 
    public static void main(String[] args) {
        String str = "w3wiki";
        int n = 5;
        System.out.println(countSubstrings(str, n));
    }
}

Python3

def count_substrings(string, n):
    count = 0
    for i in range(len(string) - n + 1):
        substring = string[i:i+n]
        # check if the current substring has length n
        if len(substring) == n:
            count += 1
    return count
 
str = "w3wiki"
n = 5
print(count_substrings(str, n))

C#

using System;
 
class GFG
{
    // Function to count the number of substrings of length n in a given string.
    static int CountSubstrings(string str, int n)
    {
        int count = 0;
         
        // Loop through the string starting from index 0 and going up to length - n.
        for (int i = 0; i <= str.Length - n; i++)
        {
            // Get the substring of length n starting at index i.
            string substring = str.Substring(i, n);
             
            // Check if the current substring has length n.
            if (substring.Length == n)
            {
                count++;
            }
        }
         
        return count;
    }
 
    static void Main()
    {
        string str = "w3wiki";
        int n = 5;
         
        // Call the function to count substrings and print the result.
        Console.WriteLine(CountSubstrings(str, n));
    }
}

Javascript

//Javascript Code
function count_substrings(str, n) {
    let count = 0;
    for (let i = 0; i <= str.length - n; i++) {
        let substring = str.substr(i, n);
        // check if the current substring has length n
        if (substring.length === n) {
            count++;
        }
    }
    return count;
}
 
//Driver's Code
let str = "w3wiki";
let n = 5;
console.log(count_substrings(str, n));

Output

Time Complexity: O(M*N), where M is the length of the input string str, since we iterate over N possible starting positions and extract a substring of length N each time.
Auxiliary Space: O(1), no extra space is required.

Count of sub-strings of length n possible from the given string

Given a string str and an integer N, the task is to find the number of possible sub-strings of length N.
Examples:

Input: str = “w3wiki”, n = 5
Output: 9
All possible sub-strings of length 5 are “geeks”, “eeksf”, “eksfo”,
“ksfor”, “sforg”, “forge”, “orgee”, “rgeek” and “geeks”.
Input: str = “jgec”, N = 2
Output: 3

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

Tags:

#substring #C++ Programs #DSA #Strings #Strings

Method 2:Efficient Approach

Method 1:Naive Approach

C++

Java

Python3

C#

Javascript

Count of sub-strings of length n possible from the given string

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