﻿ C++ : Find the last prime number occur before a number

# C++ Exercises: Find the last prime number occur before the entered number

## C++ For Loop: Exercise-8 with Solution

Write a program in C++ to find the last prime number that occurs before the entered number.

Visual Presentation:

Sample Solution :-

C++ Code :

``````#include <iostream> // Preprocessor directive to include the input/output stream header file

using namespace std; // Using the standard namespace to avoid writing std::

int main() // Start of the main function
{
int num1, ctr = 0; // Declaration of integer variables 'num1' and 'ctr' initialized to 0

// Display a message to find the last prime number before the entered number
cout << "\n\n Find the last prime number occurs before the entered number:\n";
cout << "-----------------------------------------------------------------\n";

// Prompting the user to input a number to find the last prime number before it
cout << " Input a number to find the last prime number occurs before the number: ";
cin >> num1; // Reading the number entered by the user

// Loop to find the last prime number before the entered number
for (int n = num1 - 1; n >= 1; n--) // Starting from the number before the entered number
{
for (int m = 2; m < n; m++) // Loop to check if 'n' is a prime number
{
if (n % m == 0) // If 'n' is divisible by any number other than 1 and itself
ctr++; // Increment counter
}

if (ctr == 0) // If 'ctr' is 0, 'n' is a prime number
{
if (n == 1) // If 'n' is 1, there's no prime number less than 2
{
cout << "no prime number less than 2";
break; // Break the loop
}

// Display the last prime number before the entered number
cout << n << " is the last prime number before " << num1 << endl;
break; // Break the loop
}

ctr = 0; // Reset the counter for the next iteration
}

return 0; // Indicating successful completion of the program
}
``````

Sample Output:

``` Find the last prime number occurs before the entered number:
-----------------------------------------------------------------
Input a number to find the last prime number occurs before the number:
50
47 is the last prime number before 50
```

Flowchart:

C++ Code Editor:

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