C++ Exercises: Count a substring of length 2 appears in a given string and also as the last 2 characters of the string

Last update on April 07 2025 12:56:53 (UTC/GMT +8 hours)

Count Substrings of Length 2

Write a C++ program to count the number of times a substring of length 2 appears in a given string as well as its last two characters. Do not count the end substring.

Sample Solution:

C++ Code :

#include <iostream>
using namespace std;

// Function to count occurrences of the last two characters as a substring in the input string
int test(string str)
{
    // Extract the last two characters of the input string
    string last_two_char = str.substr(str.length() - 2);
    int ctr = 0; // Initialize a counter to zero

    // Loop through the input string except for the last two characters
    for (int i = 0; i < str.length() - 2; i++)
    {
        // Check if the substring of length 2 at index 'i' matches the last two characters
        if (str.substr(i, 2) == (last_two_char))
            ctr++; // Increment the counter for each match found
    }

    return ctr; // Return the count of occurrences of the last two characters as a substring
}

// Main function
int main() 
{
    // Output the results of the test function with different input strings
    cout << test("abcdsab") << endl; 
    cout << test("abcdabab") << endl;
    cout << test("abcabdabab") << endl;
    cout << test("abcabd") << endl; 

    return 0; // Return 0 to indicate successful completion
}

Sample Output:

1
2
3
0

Visual Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C++ program to count the number of times the last two characters of a string appear elsewhere in the string without overlapping.
• Write a C++ program that reads a string and outputs the frequency of its ending two-character substring found in the rest of the string.
• Write a C++ program to determine how often the final two characters of a string appear in the string, excluding the ending occurrence.
• Write a C++ program that processes a string and counts all non-terminal appearances of its last two-letter combination.

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