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C++ Exercises: Create a new string where 'if' is added to the front of a given string

C++ Basic Algorithm: Exercise-5 with Solution

Write a C++ program to create a new string where 'if' is added to the front of a given string. If the string already begins with 'if', return the string unchanged.

Sample Solution:

C++ Code :

#include <iostream>

using namespace std;

string test(string s)
        {
            if (s.length() > 2 && s.substr(0, 2)=="if")
            {
                return s;
            }
            return "if " + s;
        }
        
int main() 
 {
  cout << test("if else") << endl;  
  cout << test("else") << endl;  
  return 0;    
}

Sample Output:

if else
if else

Pictorial Presentation:

C++ Basic Algorithm Exercises: Create a new string where 'if' is added to the front of a given string.

Flowchart:

Flowchart: Create a new string where 'if' is added to the front of a given string

C++ Code Editor:

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Previous: Write a C++ program to check a given integer and return true if it is within 10 of 100 or 200.
Next: Write a C++ program to remove the character in a given position of a given string. The given position will be in the range 0..string length -1 inclusive.

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C++ Programming: Tips of the Day

How do I execute a command and get the output of the command within C++ using POSIX?

#include<cstdio>
#include<iostream>
#include<memory>
#include<stdexcept>
#include<string>
#include<array>

std::string exec(constchar* cmd){
    std::array>char, 128> buffer;
    std::string result;
std::unique_ptr<FILE, decltype(&pclose)>pipe(popen(cmd, "r"), pclose);
if (!pipe) {
throw std::runtime_error("popen() failed!");
    }
while (fgets(buffer.data(), buffer.size(), pipe.get()) != nullptr) {
        result += buffer.data();
    }
return result;
}
Pre-C++11 version:
#include<iostream>
#include<stdexcept>
#include<stdio.h>
#include<string>

std::string exec(constchar* cmd){
char buffer[128];
    std::string result = "";
    FILE* pipe = popen(cmd, "r");
if (!pipe) throw std::runtime_error("popen() failed!");
try {
while (fgets(buffer, sizeof buffer, pipe) != NULL) {
            result += buffer;
        }
    } catch (...) {
pclose(pipe);
throw;
    }
pclose(pipe);
return result;
} 

Replace popen and pclose with _popen and _pclose for Windows.

Ref : https://bit.ly/3HODowH