Nested Loops in C++

Nested Loops in C++ with Examples:

In this article, I am going to discuss Nested Loops in C++ Language with examples. Please read our previous articles, where we discussed Binary Search in C++ with examples.

Nested Loops in C++:

Let us look at the nested ‘for’ loop. Usually, these are useful for accessing multi-dimensional arrays that are 2-D arrays or matrices. Commonly we write ‘for’ loop once. But now we are writing two ‘for’ loops, so let us write ‘for’ loop,

for(int i = 0; i < 3; i++){
    for(int j = 0; j < 3; j++){
       cout << i << “ ” << j << endl;
    }
}

So let us understand how this works and what are values will be displayed. When we say ‘cout << i << j’. ‘i’ and ‘j’ are two values initially ‘i’ is 0, 0 is less than 3. So, it will enter inside the 2nd ‘for’ loop. ‘j’ assigns 0, and j is less than 3. Here ‘i’ and ‘j’ are 0 and output will be ‘0 0’.

Nested Loops in C++ Language with examples

Now it will go up ‘j++’. ‘i’ remains the same here and ‘j’ becomes 1 then ‘j’ is less than 3 so enter 2nd for loop again and print ‘i’ and ’j’. The output will be ‘0 1’.

Nested Loops in C++ Language with examples

Next ‘j++’, ‘j’ becomes 2, and ‘i’ is still 0 and 2 is less than 3 so enter inside 2nd ‘for’ loop and print ‘i’ and ‘j’. So the output will be ‘0 2’

Nested Loops in C++ Language with examples

Then ‘j++’ j becomes 3 and now ‘j’ is not less than 3, it is equal to 3. So, nothing is done so it will come out of this for loop and still it is inside the outer for loop. Now ‘i++’ so ‘I’ becomes 1, 1 is less than 3, so it will enter inside 2nd ‘for’ loop. Initially, again ‘j’ loop starts and ‘j’ becomes 0. The same steps will repeat here. The output will be:

‘1 0’

‘1 1’

‘1 2’

Nested Loops in C++ Language

Then again ‘i’ becomes 2, and it will enter the 2nd loop then ‘j’ will again initialize as 0 and previous steps will repeat here. So the final output is,

Nested Loops in C++ Language

So, these are the values printed so if you see how it has taken the values it is just like a two-dimensional array, i.e., 00 01 02 then 10 11 12 then 20 21 22.

Nested Loops in C++

In this way nested for loop will generate the indices for the 2D array. Here ‘i’ will act like a row index and ‘j’ will act like a column index. When we will write any application on matrices, we use nested for loops.

Program to print numbers using nested loop in C++:
#include <iostream>
using namespace std;
int main()
{
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            cout << i << j << endl;
        }  
    }
}
Output:

Program to print numbers using nested loop in C++

Program to access the index of 2d Array:
#include <iostream>
using namespace std;
int main()
{
    for (int i = 0; i < 5; i++)
    {
        for (int j = 0; j < 5; j++)
        { 
            cout << "(" << i << "," << j << ") ";
        }
        cout << endl;
    }
}
Output:

Program to access index of 2d Array

In the next article, I am going to discuss Drawing Patterns using Nested Loops in C++ with examples. Here, in this article, I try to explain Nested Loops in C++ Language with examples. I hope you enjoy this Nested Loops in C++ with examples article. I would like to have your feedback. Please post your feedback, question, or comments about this article.

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