Question

Please write code in C++ and include all headers not bits/stdc:

17.10 (Occurrences of a specified character in a string) Write a recursive function that finds the number of occurrences of a specified letter in a string using the following function header.

int count(const  string& s, char a)

For example, count("Welcome", 'e') returns 2. Write a test program that prompts the user to enter a string and a character, and displays the number of occurrences for the character in the string.

(Occurrences of a specified character in a string)

Rewrite Programming Exercise 17.10 using a helper function to pass the substring high index to the function.

You need to define the following two functions. The second one is a recursive helper function.

int count(const string& s, char a)

int count(const string& s, char a, int high)

Write a test program that prompts the user to enter a string and a character, and displays the number of occurrences of the character in the string.

Input:

Welcome welcome

e

Output:

Enter a string: Welcome welcome
Enter a character: e
e occurs 4 times in Welcome welcome

Answer 1

Here is the complete c++ that implements both the variations of the functios

//These are the required header file
#include <iostream>
#include <string>
using namespace std;

//Doing it with fuction requirment of first function
int count(string &thestring, char a)
{
    //if size is 0 simply return 0
    if (thestring.size() == 0)
        return 0;
    int thecount = 0;
    //if the first character matches the required char then increase count
    if (thestring[0] == a)
        thecount++;
    //Now make a substring using the substr function [pos, pos+len)
    string temp = thestring.substr(1, thestring.size() - 1);
    //Recursively call the function
    return thecount + count(temp, a);
}

int countfunction2(const string &s, char a, int high)
{
    //if we have gone past 0 then return 0
    if (high == -1)
        return 0;
    //If the high index is char is same as the required char then recursively call with +1 addition and do high-1
    if (s[high] == a)
        return countfunction2(s, a, high - 1) + 1;
    //Other wise simply do high-1
    return countfunction2(s, a, high - 1);
}

int main()
{
    string str = "Helloteehere";
    //Calling first function
    cout << countfunction2(str, 'e', 9);
    cout << "\n";
    //Calling second function
    str = "mynameisharrypotterrrrr";
    cout << count(str, 'r');
    return 0;
}

Here is the image of the code to help understand the indentation:

//These are the required header file #include <iostream> #include <string> using namespace std; == //Doing it with fuction requirment of first function int count(string &thestring, char a) { 1/if size is o simply return o if (thestring.size() == 0) return ; int thecount = ; //if the first character matches the required char then increase count if (thestring[] a) thecount++; // Now make a substring using the substr function [pos, pos+len) string temp - thestring.substr(1, thestring.size() - 1); //Recursively call the function return thecount + count(temp, a); } int count function2(const string &s, char a, int high) { //if we have gone past then return 0 if (high == -1) return ; //If the high index is char is same as the required char then recursively call with +1 addition and do high-1 if (s[high] == a) return count function2(S, a, high 1) + 1; I/Other wise simply do high-1 return count function2(s, a, high - 1); } int main() { string str = "Helloteehere"; 1/Calling first function cout << count function2 (str, 'e', 9); cout << "\n"; // Calling second function str = "mynameisharrypotterrrrr"; cout << count(str, 'r'); return 0; }

OUTPUT:

D:\MyPrograms\C++>a 4 7 D:\MyPrograms\C++>