While Loop Examples in C++

While Loop

A while loop repeats all code in its body, also known as a while statement, as long as a specific condition is satisfied. The loop ends if or when the condition that's no longer met.

The syntax of the while loop

the syntax for a while loop is given by

while(condition)
    {
      statement(x);
     }

Examples of While Loop

Example 1: Program to find the sum and average of given numbers using a while loop.

Step 1: Start the program.

Step 2: Take the number of terms as n as inputs.

Step 3: set s=0 and i=0.

Step 4: Take a number “a” an as input.

Step 5: Perform s=s+a and i=i+1.

Step 6: Check the condition (i<n), if it is true then go to step 3, else go to step 6.

Step 7: Display s as the sum and s/n as the average.

Step 8: Exit the program.

Program

#include <iostream> 
using namespace std;
int main()
{
int n,i;
float sum = 0;
float a;
float avg;
cout<<"How many numbers ?\n";
cin>>n;
i=0;
while(i<=n-1)
     { 
      cout <<"Enter a number \n";
      cin >>a;
       sum = sum+a;
       i++; 
     }
avg = sum/n;
cout<<"sum ="<<sum<<endl;
cout<<"Average="<<avg<<endl;
}

When the program is executed, the output is:

How many numbers 
5
Enter a number:1
Enter a number:2
Enter a number:3
Enter a number:4
Enter a number: 5
Sum =15
Average =3

Explanation:
In the above program, we get the sum of all the numbers. We accept each of the numbers provided by the user into the same variable and add them to the sum variable. After that, we find the average by using (sum/number of digits) and print the average variable.

Example 2: Factorial Program in C++ using while loop.

Factorial of 5 is:
5!=5×4×3×2×1
=20×6
=120
Here 5! Is pronounced as “five factorial”, also known as “5 bang” or “5 shreik”
“!” is factorial symbol

ALGORITHM:

Step 1: Start.

Step 2: Declare variables n, factorial, and i.

Step 3: Initialize the following variables:

Factorial =1

i=1

Step 4: Read the value of n.

Step 5: Repeat the following steps until i=n

Factorial=factorial×i

i=i+1

Step 6: Display factorial.

Step 7: Stop.

Program for finding factorial of a number using WHILE loop:

#include <iostream>  
using namespace std;  
int main()  
{  
   int i,factorial=1,n;    
  cout<<"Enter a Number: ";    
  cin>>n;   
i=1;
while(i<=n) 
{    
      factorial=factorial*i; 
      i++ ;  
    }    
  cout<<"Factorial of " <<n<<" is: "<<factorial<<endl;  
  return 0;  
}  

Output:

Enter a number:
5
Factorial of 6 is 
120

Explanation

In the first iteration, i=1 and factorial =1 and n=5, i.e., (i<=n).
So, factorial =1×1=1. [factorial=factorial×i]
Now, i is increment and it becomes 2

In the second iteration, i=2 and factorial =1 and n=5i.e., (i<=n).
So, factorial =1×2=2. [factorial=factorial×i]
Now, i is increment and it becomes 3

In the third iteration, i=3 and factorial =1 and n=5, i.e., (i<=n).
So, factorial =2×3=6. [factorial=factorial×i]
Now, i is increment and it becomes 4

In the fourth iteration, i=4 and factorial =6 and n=5, i.e., (i<=n).
So, factorial =6×4=24. [factorial=factorial×i]
Now, i is increment and it becomes 5

In the fifth iteration, i=5 and factorial =24 and n=5, i.e., (i<=n).
So, factorial =24×5=120. [factorial=factorial×i]
Now, i is increment and it becomes 6

In sixth iteration, i=6 i.e (i>n), the loops get terminated and prints the answer of factorial 5 is 120.

Example 3: LINEAR SEARCH

Linear search, also known as sequential search, is a searching technique in which we have some particular data in a data structure like array data structure. In this search, we need to find a specific element called a key or number.

To identify the key, traverse all the elements of data structure from start to end one by one and comparing each data structure element to the specified key or number.

In the case of an array, we compare each element and check that if the supplied key or number is present at any index.

Assume that the array which is a linear data sctructure includes unique values, then there are two possible results.

1. A linear search is successful when the value in an array at an index matches the key, which we find in the array.

2.A linear search fails to locate a key, when the key does not exist in the data.

Algorithm:

Step 1: Start.

Step 2: Declare array a and variables count,I, num.

Step 3: Input the elements in the array. 

Step 4: Input for count, the num to be searched.

Step 5: If (a[i] = num), then display Number is present at location (i+1)

Step 6: if (i=count), then display Number is not present in the array

Step 7: Stop.

Program:

#include <iostream> 
using namespace std;
int main() 
{
        int input[100], count, i, num ;
         cout << "Enter Number of Elements in Array\n";
         cin >> count;
         cout << "Enter"<< count<<"numbers\n";
                 // Read array elements 
    i=0;
 while (i<count)
              { 
                 cin>>input[i];
                i++;
              }
         cout << "Enter a number to serach in Array\n";
         cin>>num;


         // search num in inputArray from index 0 toelementCount-1 //
         i=0;
        while(i<count)
                {
                        if(input[i] == num)
                              {
                               cout << " TheElement found at index " << i;
                                i++;
                               break;
                              }
                }
           if(i==count)
                  {
                      cout << "Element Not Present in Input Array\n";
                  }
          return 0;
     }

Output is:

Enter the number of Elements in the Array
6
Enter 5 numbers 
12  23  25  37  45  14
Enter a number to search in the Array
37
The Element found at index 3