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For Loop Examples in C++

For Loop

A for loop is a repetitive control structure that allows you to create a loop to execute a specific number of times efficiently.

The syntax of for loop

In C++, a for loop is written as

for (initialize; condition; increment) 
 {
 statement(x);
}

Examples of For Loop


Example 1: Program to find the sum and average using FOR LOOP:
Algorithm:

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;
float sum=0;
float a;
float avg;
cout <<"How many numbers? \n";
cin >>n;
for (int i=0; i<=n-1; ++i)
     { 
        cout << "Enter a number \n";
       cin >> a;
      sum = sum+a;
   }
Avg = sum/n;
cout << "sum =" << sum <<endl;
cout << "Average =" <<avg <<endl;
return 0;
}

Output:

How many numbers 
5
Enter a number:5
Enter a number:10
Enter a number:15
Enter a number:20
 Enter a number: 25
Sum =75
Average =15

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: Program to add two matrices using for loops
Algorithm to add two matrices:

Step 1: Start the program.

Step 2: Declare one[50][50], two[50][50], sum[50][50].

Step 3: Read rols, colms, p, a[ ][ ], b[ ][ ].

Step 4: If i<rows is true, then control returns to step 8 and if j<colms is true then control return to step 7.

Step 5: C[i][j] = A[i][j] + B[i][j].

Step 6: Perform the operation j = j+1.

Step 7: Perform the operation i=i+1.

Step 8: Print C[ I ][ j ].

Step 9: Exit the program.

Program to add 2D array matrices:

#include<iostream>
using namespace std;  
int main()
{ 
    int rows, cols, i, j; 
    int one [50][50], two [50][50], sum [50][50];
    cout <<"EnterRows and Columns of Matrix\n";
    cin >>rows>>cols;
    cout << "Enter first Matrix of size " <<rows << " X " << cols; 
          // Input first matrix*/ 
    for(i=0; i<rows; i++)
       { 
           for(j=0; j<cols; j++ )
                {  
                      Cin >> one[i][j];
                } 
   }      
          // Input second matrix
 cout << "\nEnter second Matrix of size " << rows << " X " << cols; 
      for(i=0; i<rows; i++)
          {
                  for(j=0; j<cols; j++)
                           { 
                                cin >> two[i][j];
                            } 
        }
 /* adding corresponding elements of both matricessum[i][j] = one[i][j] + two[i][j]*/
      for(i=0; i<rows; i++)
        { 
            for(j=0; j<cols; j++)
                 { 
                        sum[ i ][ j ] = one[ i ][ j ] + two[ i ][ j ];
               }
          } 
            
   for(i=0; i<rows; i++)
       {
           for(j=0; j<cols; j++)
             {
                   cout << sum[ i ][ j ]<< " ";
            } 
   cout <<"\n";
      } 
return 0; 
}

The output of the program:

Enter the number of rows and columns
3×3
Enter the first matrix 
11 12 13
14 15 16 
17 18 19   
Enter the second matrix 
9 8 7 
6 5 4 
3 2 1
Sum of given two matrices
20 20 20 
20 20 20 
20 20 20

Explanation of the program of the addition of two matrices:

1. First, we use 2D arrays to initialize the three matrices A, B, and c.
2. Both matrices A and B have the same number of rows and columns.

3. Using nested for loop, we insert elements of matrices A entered by the user.

4. Using nested for loop, we print elements of matrices A on the output screen.

5. Using nested for loop, we insert elements of matrices B entered by the user.

6. Using nested for loop, we print elements of matrices B on the output screen.

7. Using the nested for loop, we combine the components of matrices A and B and store them in matrix c.

8. All the elements of matrix c are printed on the output console.

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.

C++ Program to search any element or number in an array

#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 
         for(i = 0; i < count; i++)
              { 
                 cin>>input[i];
              }
         cout<<"Enter a number to serach in Array\n";
         cin>>num;


         // search num in inputArray from index 0 toelementCount-1 //


         for(i = 0; i < count; i++)
                 {
                        if(input[i] == num)
                              {
                               cout<<"Element found at index"<< i;
                               break;
                              }
                }
           if(i==count)
                  {
                      cout<<"Element Not Present in Input Array\n";
                  }
          return 0;
     }

Output:

Enter the number of Elements in the Array
5
Enter 5 numbers
11 22 33 44 55
Enter a number to search in the Array
33
 element found at index 2

Explanation:

Take the user's input for the number of elements in the array and save it in the count variable. Take N numbers from the user and store them in an array using a loop (Let the name of array as input[100]).

Now, enter the element to be searched in an specified. Let the element or key as (num).

Scan the input array from index 0 to N-1 using a for loop and compare num with each array element. If (num) matches with any array element, then print "Element found at particular index", otherwise print "Element Not Present."

Advantages:

Recent powerful computers can search small to medium arrays quickly. The list does not need to be sorted. Linear searching, unlike binary searching, does not necessitate the use of an ordered list. Insertions and deletions have no effect.

Example 4: FACTORIAL PROGRAM IN C++ USING FOR 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 for loop:

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

Output:

Enter a number:
5
Factorial of 5 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.



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