🔄 While Loop in C++
The while loop executes a block of code repeatedly as long as the condition is true.
🔹 Syntax
while (condition) {
// Code to execute
}
- The condition is checked before each iteration.
- The loop runs until the condition becomes false.
1️⃣ Armstrong Number using While Loop
📌 An Armstrong number is a number where the sum of its digits, each raised to the power of the number of digits, equals the number itself.
👉 Example: 153 = 1³ + 5³ + 3³ = 153
#include <iostream>
#include <cmath>
using namespace std;
int main() {
int num, originalNum, remainder, result = 0, n = 0;
cout << "Enter a number: ";
cin >> num;
originalNum = num;
while (originalNum != 0) {
originalNum /= 10;
n++; // Count digits
}
originalNum = num;
while (originalNum != 0) {
remainder = originalNum % 10;
result += pow(remainder, n);
originalNum /= 10;
}
if (result == num)
cout << num << " is an Armstrong number." << endl;
else
cout << num << " is not an Armstrong number." << endl;
return 0;
}
🔹 Output
Enter a number: 153
153 is an Armstrong number.
2️⃣ Decimal to Binary in C++
📌 Convert a decimal number to binary using a while loop.
#include <iostream>
using namespace std;
int main() {
int num, binary = 0, place = 1, remainder;
cout << "Enter a decimal number: ";
cin >> num;
while (num > 0) {
remainder = num % 2;
binary += remainder * place;
place *= 10;
num /= 2;
}
cout << "Binary: " << binary << endl;
return 0;
}
🔹 Output
Enter a decimal number: 10
Binary: 1010
3️⃣ Printing Even & Odd Numbers
📌 Print even & odd numbers separately using a while loop.
Even Numbers
#include <iostream>
using namespace std;
int main() {
int i = 2;
while (i <= 10) {
cout << i << " ";
i += 2;
}
return 0;
}
🔹 Output
2 4 6 8 10
Odd Numbers
#include <iostream>
using namespace std;
int main() {
int i = 1;
while (i <= 10) {
cout << i << " ";
i += 2;
}
return 0;
}
🔹 Output
1 3 5 7 9
4️⃣ Printing Positive & Negative Numbers
📌 Separate positive and negative numbers from an array using a while loop.
#include <iostream>
using namespace std;
int main() {
int arr[] = {-10, 15, -3, 8, -7, 12, 5, -1};
int size = sizeof(arr) / sizeof(arr[0]);
int i = 0;
cout << "Positive numbers: ";
while (i < size) {
if (arr[i] > 0) {
cout << arr[i] << " ";
}
i++;
}
i = 0;
cout << "\nNegative numbers: ";
while (i < size) {
if (arr[i] < 0) {
cout << arr[i] << " ";
}
i++;
}
return 0;
}
🔹 Output
Positive numbers: 15 8 12 5
Negative numbers: -10 -3 -7 -1
5️⃣ Prime Numbers between Two Numbers
📌 Find all prime numbers in a given range using a while loop.
#include <iostream>
using namespace std;
bool isPrime(int num) {
if (num < 2) return false;
int i = 2;
while (i * i <= num) {
if (num % i == 0) return false;
i++;
}
return true;
}
int main() {
int start, end;
cout << "Enter range (start end): ";
cin >> start >> end;
cout << "Prime numbers: ";
while (start <= end) {
if (isPrime(start)) {
cout << start << " ";
}
start++;
}
return 0;
}
🔹 Output
Enter range (start end): 10 20
Prime numbers: 11 13 17 19
6️⃣ Find Prime or Composite
📌 Check if a number is prime or composite.
#include <iostream>
using namespace std;
int main() {
int num, i = 2, isPrime = 1;
cout << "Enter a number: ";
cin >> num;
if (num <= 1) {
cout << num << " is neither prime nor composite.";
return 0;
}
while (i * i <= num) {
if (num % i == 0) {
isPrime = 0;
break;
}
i++;
}
if (isPrime)
cout << num << " is a Prime number.";
else
cout << num << " is a Composite number.";
return 0;
}
🔹 Output
Enter a number: 7
7 is a Prime number.
7️⃣ Printing Numbers using While Loop
📌 Print numbers from 1 to N.
#include <iostream>
using namespace std;
int main() {
int n, i = 1;
cout << "Enter a number: ";
cin >> n;
while (i <= n) {
cout << i << " ";
i++;
}
return 0;
}
🔹 Output
Enter a number: 5
1 2 3 4 5
8️⃣ Tables using While Loop
📌 Print the multiplication table of a number.
#include <iostream>
using namespace std;
int main() {
int num, i = 1;
cout << "Enter a number: ";
cin >> num;
while (i <= 10) {
cout << num << " x " << i << " = " << num * i << endl;
i++;
}
return 0;
}
🔹 Output (if input is 3)
3 x 1 = 3
3 x 2 = 6
...
3 x 10 = 30
9️⃣ Reverse Tables using While Loop
📌 Print the reverse multiplication table.
#include <iostream>
using namespace std;
int main() {
int num, i = 10;
cout << "Enter a number: ";
cin >> num;
while (i >= 1) {
cout << num << " x " << i << " = " << num * i << endl;
i--;
}
return 0;
}
🔹 Output (if input is 3)
3 x 10 = 30
3 x 9 = 27
...
3 x 1 = 3
📌 Summary
✔ while loops run as long as the condition is true.
✔ break exits the loop.
✔ continue skips the current iteration.
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