Nested if in C++

If is a type of condition checking in which a condition turns out to be true a block of statements is executed.

Syntax:

// if base_condition is true
// every inside the { } block will be executed
if (base_condition)
{
    statement 1...............
    statement 2 ..............
}

Example

C++

// C++ Program demonstrate
// use if-else condition
#include <iostream>
using namespace std;

int main()
{
    int a = 6, b = 5;
    if (a > b) {
        cout << "True" << endl;
    }
}

Output

True

What is Nested If?

When a number of if blocks are present one after another with the same scope (the same scope means under one { } block), then that condition is termed as a Nested if condition. If the first condition is True, we go into the next if condition and the subsequent condition is checked until we get a false condition, and the checking stops.

Syntax:

// if base_condition is true control goes to base_condition1
if ( base_condition) 
{
    // if base_condition is true control goes to base_condition2
    if(base_condition1) 
    {
        if(base_condition2) 
            ..........................
        ..........................
    }
}

Example 1:

C++

// C++ Program to
// Nested-if conditions
#include <iostream>
using namespace std;

int main()
{

    int a = 20, b = 10, c = 2;

    // if this condition satisfies then
    // control goes to next if condition
    if (a > b) {
        // if this condition also turns out to be
        // true then the statements under
        // this block will get executed
        if (a > c) {
            cout << " a is the largest " << endl;
        }
    }
    return 0;
}

Output

 a is the largest 

Example 2:

C++

// C++ Program to
// Nested-if conditions
#include <iostream>
using namespace std;

int main()
{

    int a = 20, b = 10, c = 2;

    if (a == 20) {
        if (b == 10) {
            if (c == 2) {
                cout << "Sandeep Sir is Great!!" << endl;
            }
        }
    }
    return 0;
}

Output

Sandeep Sir is Great!!

Example 3:

C++

// C++ Program to
// Nested-if conditions
#include <iostream>
using namespace std;

int main()
{

    int a = 20, b = 10, c = 1;
    // this condition is true
    if (a == 20) {
        // this condition is also true
        if (b == 10) {
            // but this condition is false hence
            // we get out of the nested block
            if (c == 2) {
                cout << "Sandeep Sir is Great!!" << endl;
            }
        }
    }
    cout << "gfg\n";

    return 0;
}

Output

gfg

Example 4:

C++

// C++ Program to demonstrate
// Nested-if condition
#include <iostream>
using namespace std;

int main()
{

    int a = 220, b = 10, c = 1;
    // this condition is itself false we don't
    // get inside the nesting if block
    if (a == 20) {
        if (b == 10) {
            if (c == 2) {
                cout << "Sandeep Sir is Great!!" << endl;
            }
        }
    }
    cout << " No nested if condition is executed \n ";
    return 0;
}

Output

 No nested if condition is executed 
 

Time complexity: O(1).

Auxiliary space: O(1).