Iteration Statements in C++

Types Of Entry Controlled Loop 

The for Loop

A for loop is a repetition manipulate structure for loop is a repetition control structure that lets us write a circle that is performed a particular variety of instances. The loop enables us to perform n number of steps together in one line.

Syntax:

for(initialize; condition; update) 
{
  //body of the for loop
}

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Note that initializes, situations, and replaces are optional expressions and are always specified in parentheses. All of the three words are separated using semicolons. The semicolons are mandatory and, for this reason, can't be excluded even if all of the three expressions are unnoticed.

The following example:

#include <iostream>
using namespace std;


int main()
{
    int i, j;
    for ( i = 5, j = 10 ; i + j < 20; i++, j++ ) {
        cout << "i + j = " << (i + j) << '\n';
    }
}

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Output:

i + j = 15
i + j = 17
i + j = 19

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The while Loop

The loop is used to perform looping operations in situations where the number of iterations is not recognized in advance. Unlike the for-loop, the while loop is non-deterministic.

Syntax

while(condition) 
{
  // body of while loop
}

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Unlike loops in which initialize and replace expressions are specific, loops no longer specify any express initialize and replace phrases. This means that the control variable should be declared and initialized in advance of the while loop and needs to be up to date inside the frame of the same time as the loop.

The while loop executes so long as the condition evaluates to be authentic. If the condition evaluates to false inside the first new release, the frame of the while loop never executes.

While a loop can have more than one expression in its condition, such multiple terms must be separated using commas and are done within the order in their look.

The following example

#include <stdio.h>
Using namespace std;
  
int main()
{
    int i = 1;
    while (i < 7)
    {
        printf( "Coding Ninjas\n");    
        i++;
    }
   return 0;
}

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Output:

Coding Ninjas
Coding Ninjas
Coding Ninjas
Coding Ninjas
Coding Ninjas
Coding Ninjas

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Also Read - C++ Interview Questions

Types of Controlled Exit Loop

The do-while loop

In the do-while loops, the loop execution is terminated on the idea of the test condition. The principal difference between the do-while loop and the while loop is that in the do-while loop the situation is tested on the quit of loop frame, i.e., do at the same time as the loop goes out managed whereas the other loops are entry controlled loops. In the do-while loop, the loop body will execute at least as soon as the test condition.

Syntax:

do
{
   statement ;
}
while(test-expression);

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The following example:

#include <iostream>
using namespace std;
  
int main()
{
    int i = 2; 
  
    do
    {
        cout << "Coding Ninjas\n";
        i++;
   } 
   while (i < 1); 
   return 0;
}

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Output:

Coding Ninjas

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Let's watch a quick video on Loops in C++ to fully comprehend whatever we have read so far, and don't forget to follow Data Structures and Algorithms in C++, a free and comprehensive video series by Coding Ninjas, that covers each topic thoroughly.

Frequently Asked Questions

1. In programming, what is iteration?
   Iteration is the repetition of steps within a program.
    
2. Why is iteration necessary?
   Iteration is essential because it simplifies code by removing duplicated steps.
    
3. Which statements are used to implement entry-controlled iteration?
   FOR and WHILE statements are used to implement iteration.
    
4. What are the two types of iteration?
   The two types of iteration are Entry-controlled loops and Exit-controlled loops.

Key Takeaways

We learned about loops in C++ and their types. We saw in detail how to use for, while & do-while Loops and their syntax. 

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