Question

Assignment:

Write an interactive C++·program to determine a type of a triangle based on three sides.

• Have a user input the length of three sides of a triangle. Allow the user to enter the sides in any order.
• Determine if the entered sides form a valid triangle. The triangle may not have negative sides. The sum of any two sides must be greater than the third side to form a triangle.
• Determine if the entered sides are part of a scalene, isosceles, or equilateral triangle. Using the Pythagorean Theorem, determine if the scalene or isosceles triangle is a right triangle. (A squared plus B squared equals C squared, where C is the hypotenuse.)
• Adequately check entered data for validity. Use adequate test data to process all valid data and representative combinations of invalid data.
• Label output clearly.
• Be sure your output printout contains user prompts and what was entered by the user in addition to the results of your program processing.
• Test your program thoroughly

Input

Length of three sides of a triangle.

Output

Length of three sides; type of triangle; whether or not a triangle is a right triangle. Output an appropriate error message for invalid lengths entered for one or more sides or side lengths that cannot form a triangle.

Answer 1

C++ code:

#include <iostream>
#include <bits/stdc++.h>
using namespace std;

// function to check if the valid triangle can be formed
bool is_valid(int a, int b, int c){
    if ( a+b <= c) return false;
    if ( b+c <= a) return false;
    if ( c+a <= b) return false;
    return true;
}


int main() {

    // Take input
    float a, b, c;
    cout << "Enter the three sides of a triangle separated by a space: ";
    cin >> a >> b >> c;

    // Invalid lengths
    if ( a <= 0 || b <= 0 || c <= 0 ){
        cout << "Invalid lengths have been entered" << endl;
    }
    
    // Invalid triangle
    else if (is_valid(a, b, c) == false){
        cout << "The given lengths cannot form a triangle" << endl;
    }

    // Equilateral Triangle
    else if ( a == b && b == c){
        cout << a << " " << b << " " << c << "; " << "Equilateral Triangle; " << "Not a right triangle" << endl; 
    }

    // Isosceles Triangle
    else if ( a == b || b == c || c == a){
        if ( pow(a,2) + pow(b,2) == pow(c,2) || pow(b,2) + pow(c,2) == pow(a,2) || pow(c,2) + pow(a,2) == pow(b,2) ){
            cout << a << " " << b << " " << c << "; " << "Isosceles Triangle; " << "Is a right triangle" << endl; 
        }else{
            cout << a << " " << b << " " << c << "; " << "Isosceles Triangle; " << "Not a right triangle" << endl; 
        }
    }

    // Scalene Triangle
    else{
        if ( pow(a,2) + pow(b,2) == pow(c,2) || pow(b,2) + pow(c,2) == pow(a,2) || pow(c,2) + pow(a,2) == pow(b,2) ){
            cout << a << " " << b << " " << c << "; " << "Scalene Triangle; " << "Is a right triangle" << endl; 
        }else{
            cout << a << " " << b << " " << c << "; " << "Scalene Triangle; " << "Not a right triangle" << endl; 
        }
    }

    return 0;
}

Sample execution of the above code: