C++ program to calculate the area, perimeter and diagonal of a square has been given below. If length of the side of a square is $s~ unit$, the area, perimeter and diagonal of that square would be $s^2~\text{unit}^2$, $4s~\text{unit}$ and $s\sqrt{2}~\text{unit}$ respectively.

For example, if length of the side of a square is $5~cm$, the area would be $5^2 = 25~\text{cm}^2$ while the perimeter would be $4 \cdot 5 = 20~\text{cm}$. The diagonal will be calculated as $5\cdot \sqrt{2} = 7.071 ~\text{cm}$

In the following section, the algorithm, pseudocode and time-complexity of the program have also been covered.

## 1. Algorithm to calculate the area, perimeter and diagonal of a square

1. Take the length of side $s$ as input.

2. Declare $s^2$ as the area of the square

3. Declare $4s$ as the perimeter of the square

4. Declare $s\sqrt{2}$ as the diagonal of the square

## 2. Pseudocode to calculate the area, perimeter and diagonal of a square

Input : Length of side $s$

Output : Area $A$, Perimeter $P$ and Diagonal $D$ of the square

1. Procedure areaPerimeterDiagonal($s$):

2. $A = s^2$

3. $P = 4s$

4. $D = s\sqrt{2}$

5. Return $A, P, D$

6. End Procedure

## 3. Time complexity to calculate the area, perimeter and diagonal of a square

Time Complexity: O(1)

## 4. C++ Program to calculate the area, perimeter and diagonal of a square

Code has been copied
/***********************************
alphabetacoder.com
C++ program to calculate the area
,perimeter and diagonal of a square
************************************/

#include <iostream>
#include <cmath>

using namespace std;

int main() {
// declare variables
float s, a, p, d;

// take input
cout << "Enter the length of side of the square: ";
cin >> s;

// calculate area
a = s * s;
// calculate perimeter
p = 4 * s;
// calculate diagonal
d = s * sqrt(2);

// display result
cout << "Area: " << a << endl;
cout << "Perimeter: " << p << endl;
cout << "Diagonal: " << d << endl;

return 0;
}


Output

Enter the length of side of the square: 10.5

Area: 110.25

Perimeter: 42

Diagonal: 14.8492