Mayank Gupta

In the previous article, we have discussed about C++ Program to Calculate Sum of First N Natural Numbers. Let us learn how to find Largest Number Among Three Numbers in C++ Program.

Method to find the largest number among 3 numbers in c++

In this article, we see different methods by which we can largest of 3 numbers using c++. Let see all the methods one by one.

• Using if statements
• Using if-else statement
• Using nested if-else statement
• Using Ternary operator

Method 1-Using if statements

In this method, we use three if statements for all three numbers. In the first, if statement we will compare the first number with the second and third numbers and if it is greater than both the number then we will say number 1 is the largest. In the second if statement we will compare the second number with the first and third numbers and if it is greater than both the number then we will say number 2 is the largest. In the third, if statement we will compare the third number with the second and first numbers and if it is greater than both the number then we will say number 3 is the largest. Let write the code for this.

#include <iostream>
using namespace std;

int main() {
    // your code goes here
    int n1=10,n2=12,n3=9;
     if(n1 >= n2 && n1 >= n3)
        cout << "Largest number: " << n1;

    if(n2 >= n1 && n2 >= n3)
        cout << "Largest number: " << n2;
    
    if(n3 >= n1 && n3 >= n2)
        cout << "Largest number: " << n3;
    return 0;
}

Output

Largest number: 12

Here we see that 12 is the largest among the 3 numbers.

Method 2-Using if-else statement

There is a flaw in the first method because in the first method all the if statement runs. Suppose if we get that number 1 is the greatest is greatest in first if statement then in that case also all if statement runs. So to improve this we can use the if-else statement. In if-else statements, if one condition pass then we will not go to further statements. Let write the code for this.

#include <iostream>
using namespace std;

int main() {
    
    int n1=10,n2=12,n3=9;
     if((n1 >= n2) && (n1 >= n3))
        cout << "Largest number: " << n1;
    else if ((n2 >= n1) && (n2 >= n3))
        cout << "Largest number: " << n2;
    else
        cout << "Largest number: " << n3;
    return 0;
}

Output

Largest number: 12

Method 3-Using nested if-else statement

This method is a more efficient version than the first two methods. Let write a code for this.

#include <iostream>
using namespace std;

int main() {
    
    int n1=10,n2=12,n3=9;
     if (n1 >= n2) {
        if (n1 >= n3)
            cout << "Largest number: " << n1;
        else
            cout << "Largest number: " << n3;
    }
    else {
        if (n2 >= n3)
            cout << "Largest number: " << n2;
        else
            cout << "Largest number: " << n3;
    }

    return 0;
}

Output

Largest number: 12

Method 4-Using Ternary operator

The ternary operator is a way of using an if-else statement in one line.So by using the ternary operator we can reduce our code line with the same logic that we discuss above. Let write the code for this.

#include <iostream>
using namespace std;

int main() {
    
    int n1=10,n2=12,n3=9;
     int max = (n1 > n2) ?
          (n1 > n3 ? n1 : n3) :
          (n2 > n3 ? n2 : n3);
    cout << "Largest number among "
         << n1 << ", " << n2 << " and "
         << n3 << " is " << max << "." ;

    return 0;
}

Output

The largest number among 10, 12, and 9 is 12.

So these are the methods to find the largest among 3 numbers in c++.

In the previous article, we have discussed about C++ Program to Convert Decimal Number to Binary Number. Let us learn how to Convert Octal Number to Decimal Number in C++ Program.

Methods to Convert Octal Numbers to Decimal Numbers in C++

In this article, we will discuss different methods of converting octal to decimal numbers in c++. The list of the methods that we will discuss is given below.

• Using Loop with arithmetic operator
• Using pre-defined function

Let discuss the basic idea for converting octal to a decimal number which will help us later in writing the code. Let discuss the approach with the help of an example. Suppose the octal number is 67 then its decimal form is 55. We will write 67 as 6*(8^1)+7*(8^0) which is equivalent to 55. So here we see we extract the digit of decimal number and multiply the digit with the power of 8 in increasing order. This means the first digit is multiplied with 8 to the power 0 while the second digit is multiplied with 8 to the power 1 and so on. So this is the intuition. Let’s discuss different methods to do it.

Method 1-Using Loop with arithmetic operator

In this approach, we will take the help of a loop and modulo(%) and division(/) operator to extract the digit of the binary number. When we extract the digit we will simply multiply the digit with a power of 8 and stored the result in the variable. Let’s write the code for this.

#include <bits/stdc++.h>
using namespace std;


int convertOctalToDecimal(long long n)
{
    int decimalNumber = 0, i = 0, rem;
    while (n!=0)
    {
        rem = n%10;
        n /= 10;
        decimalNumber += rem*pow(8,i);
        i++;
    }
    return decimalNumber;
}

int main()
{
    long long n=67;
    cout << n << " in octal is " << convertOctalToDecimal(n) << " in decimal";
    return 0;
}

Output

67 in octal is 55 in decimal

Method 2-Using pre-defined function

In c++ there is a pre-defined function that is used to convert octal to decimal numbers. Here we are talking about stoi() function. Let us see what the stoi() function is.stoi() stands for the string to integer, it is a standard library function in C++ STL, it is used to convert a given string in various formats (like binary, octal, hex, or a simple number in string formatted) into an integer. Let’s write the code for this.

#include <bits/stdc++.h>
using namespace std;

int main()
{
    string n="67";
    cout << n << " in octal is " <<  stoi(n, 0, 8) << " in decimal";
    
    return 0;
}

Output

67 in octal is 55 in decimal

So these are the methods to convert octal numbers to decimal numbers in c++.

In the previous article, we have discussed about C++ Program to Display Fibonacci Series. Let us learn how to find factorial in C++ Program.

Methods to find factorial of a given number in c++

In this article, we discuss different methods of how we can find the factorial of a given number in c++. The list of methods that we will discuss is given below.

• Iterative approach
• Using Recursion
• Using Dynamic Programming

Before discussing the different methods let first understand what a factorial of the given number is. Factorial of a non-negative integer is the multiplication of all integers smaller than or equal to n. For example factorial of 6 is 6*5*4*3*2*1 which is 720.

Now we will discuss different methods to find the factorial of a given number.
<h3>Method 1-Iterative approach

As we discussed above that the factorial of a non-negative integer is the multiplication of all integers smaller than or equal to n. Hence we simply apply a for loop from 1 to a given number a store their multiplication in a variable and then print it. Let’s write the code for this.

#include <iostream>
using namespace std;

int main() {
    int res = 1, i,n=6;
    for (i = 1; i <= n; i++)
    {
        res *= i;
    }
    cout<<"Factorial of given number "<<n<<" is "<<res;
    
    return 0;
}

Output

Factorial of given number 6 is 720

Method 2-Using Recursion

Let analyze how we can calculate the factorial of a given number using recursion.

Suppose we want to calculate the factorial of the number 6. So we can write it as:-

factorial(6)=6*5*4*3*2*1  and if we analyze that 5*4*3*2*1 is also the factorial of number 5 so we can break factorial of 6 into factorial(6)=6* factorial(5) So that’s how we can call the recursive function. Let write the code for this.

#include <iostream>
using namespace std;
int factorial(unsigned int n)
{
    if (n == 0)
        return 1;
    return n * factorial(n - 1);
}
int main() {
    int n=6;
    cout<<"Factorial of given number "<<n<<" is "<<factorial(6);
    
    return 0;
}

Output

Factorial of given number 6 is 720

Method 3-Using Dynamic Programming

The problem with the above recursive is that we have to call the recursive function for a particular number multiple times. Here Dynamic programming solves this problem. Instead of calling a recursive function for a given number again and again we store the result of that number in an array and when this number we directly return its value from the array instead of calculating the value again. Let’s write the code for this.

#include <iostream>
using namespace std;
int result[1000] = {0};
int factorial(int n) {
   if (n >= 0) {
      result[0] = 1;
      for (int i = 1; i <= n; ++i) {
         result[i] = i * result[i - 1];
      }
      return result[n];
   }
}
int main() {
   int n=6;
   cout<<"Factorial of a given number "<<n<<" is "<<factorial(n);
   return 0;
}

Output

Factorial of a given number 6 is 720

So these are the methods to calculate the factorial of a given number in c++.

Methods to get filename from a path with or without extension in c++

C++ get file name: In this article, we discuss the different methods to get filename from a path with or without extension in c++. Let’s see c get filename from path with extension, c get filename from path without extension, c remove path from filename, c find all files in directory with extension, c iterate through files in a directory, c filesystempath to string, c++ get filename from path, c get file path, c++ iterate through files in a directory, c++ get file path, c filesystem::path to string, How to get filename from a path with or without extension in c++. The method that we discuss are given below:-

• Using string functions
• Using C++17 Filesystem library

Let’s first understand what we will be going to do in this article. Suppose there is a path name p="/home/user/c++/program.c++" then in this example filename with extension is program.c++ and filename without extension is program. So we will be writing code in c++ to do this task.

Let’s understand all the methods one by one.

Method 1-Using string functions

C++ get file extension: In this method, we use the string in c++ to do the task. We will use different functions that are used in c++ strings to extract the filename. Let see this with the help of an example.

#include <iostream>
#include <string>

using std::string;
string getFileNameWithExtension(const string& s) {
char sep = '/';
#ifdef _WIN32
sep = '\\';
#endif
size_t i = s.rfind(sep, s.length());
if (i != string::npos) 
{
string filename = s.substr(i+1, s.length() - i);
string rawname = filename.substr(0, s.length()); 
return(rawname);
}

return("");
}

string getFileNameWithoutExtension(const string& s) {
char sep = '/';
#ifdef _WIN32
sep = '\\';
#endif
size_t i = s.rfind(sep, s.length());
if (i != string::npos) 
{
string filename = s.substr(i+1, s.length() - i);
size_t lastindex = filename.find_last_of("."); 
string rawname = filename.substr(0, lastindex); 
return(rawname);
}

return("");
}

int main() {

string path = "/home/user/c++/program.c++";
string filename_with_extension = getFileNameWithExtension(path);
string filename_without_extension= getFileNameWithoutExtension(path);
std::cout << "The file name with extension  is \"" << filename_with_extension  << "\"\n";
std::cout << "The file name without extension  is \"" << filename_without_extension << "\"\n";
}

Output

The file name with extension is "program.c++"
The file name without extension is "program"

Method 2-Using C++17 Filesystem library

Java get filename without extension: The Filesystem library provides facilities for performing operations on file systems and their components, such as paths, regular files, and directories. So here we will use the Filesystem library to get filename from a path with and without extension. Let’s write code for this.

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
 
int main()
{
    std::cout << "The file name with extension  is " <<fs::path( "/home/user/c++/program.c++" ).filename() << '\n';
    std::cout << "The file name without extension  is " <<fs::path( "/home/user/c++/program.c++" ).stem() << '\n';
        
}

Output

The file name with extension is "program.c++"
The file name without extension is "program"

So these are the methods to get filename with and without extension in c++.

C++ reverse number: In the previous article, we have discussed about C++ Program to Calculate Power of a Number. Let us learn how to Reverse a Number in C++ Program.

Methods to Reverse a Number in C++

How to reverse a number c++: In this article, we will see different methods of how we can reverse a number in c++. Let see all the methods one by one.

• Using while loop
• By converting number to string

Method1-Using while loop

get4321.com: In this method, we extract the digit of a number a through this we will make a new number which is the reverse of the given number. Let’s write the code to understand this.

#include <iostream>
using namespace std;

int main() {
    int n, reversedNumber = 0, remainder;
    n=1234;
    while(n != 0) {
        remainder = n%10;
        reversedNumber = reversedNumber*10 + remainder;
        n /= 10;
    }
    cout << "Reversed Number = " << reversedNumber;

    return 0;
}

Output

Reversed Number = 4321

Now lets see how this work. Suppose our number is 1234.

Iteration1- remainder-4  reversedNumber=(0*10)+4=4    number=1234/10=123

Iteration2- remainder-3  reversedNumber=(4*10)+3=43    number=123/10=12

iteration3- remainder-2   reversedNumber=(43*10)+2=432   number=12/10=1

iteration4- remainder-1    reversedNumber=(432*10)+1=4321   number=1/10=0

As the number become 0 so we come out of the loop and we get 4321 as our reversed number.

Method 2-By converting number to string

In this method first, we convert our number to a string. For this we use inbuilt method in c++ to_string().Then we reverse the string using the reverse() method in c++. And then we convert that reverse string again to a number using stoi() method. Let write the code for this.

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n, reversedNumber = 0, remainder;
    n=1234;
    string s=to_string(n);
    reverse(s.begin(),s.end());
    n=stoi(s);
    cout << "Reversed Number = " << n;
    return 0;
}

Output

Reversed Number = 4321

So these are the methods to reverse a number in c++.