Can't find logic error

crystalattice · #1 23-May-2004, 15:11

The code below creates a simple boolean output for determining the type of triangle you have based on the length of the sides, i.e. equilateral, isosceles, or scalene. The code works except for determining isosceles; if only 2 sides are the same length, all I'm told is that it's a triangle.

I've tried different ways of doing the AND/OR logic and using loops, switches, etc. Does anyone see my logic error? Thanks.

CPP / C++ / C Code:

/*
Purpose:  from 3 real numbers, determine if they represent an 
equilateral, isosceles, or scalene triangle
*/

#include <iostream>

using namespace std;

int main()
{
	//Input
	cout << "Enter 3 numbers\n";
	int n1, n2, n3;
	cin >> n1
		>> n2
		>> n3;
	
	//Calculations
	bool triangle, equilateral, isosceles, scalene;
	
	if (((n1+n2)>n3) || ((n2+n3)>n1) || ((n3+n1)>n2))
		triangle = true;
	else triangle = false;
	
	if ((triangle == true) && ((n1!=n2)&&(n2!=n3)&&(n3!=n1)))
		scalene = true;
	else scalene = false;
	
	if ((triangle == true) && ((n1==n2)&&(n2==n3)))
		equilateral = true;
	else equilateral = false;
	
	if ((triangle == true) && (((n1==n2)&&(n1==n3))||((n1==n2)&&(n2==n3))))
		isosceles = true;
	else isosceles = false;
	
	
	
	//Output
	cout << "\nTriangle " << triangle
		<< "\nEquilateral " << equilateral
		<< "\nIsosceles " << isosceles
		<< "\nScalene " << scalene;
	return 0;
}

machinated · #2 23-May-2004, 17:19

1. you have not initialized your boolean variables.
using uninitialized variables may cause your program to malfunction.
also if you were to initialize your boolean variables to false, you would be able to get rid
of those else statements where you define them to be false each time.

2. your triangle determination logic is flawed. type in 1 1 0 or 1 1 2
it shouldnt form a triangle, but it does. fix your statement. change the ORs to ANDs.

3. your isosceles triangle determination logic is flawed.
a. Apparently when your triangle turns out to be equilateral, it's also an isosceles - do you want it to do that?
b. you are checking for equilateral triangles in your isosceles statement. you need to change it to reflect the isosceles triangle properties:

CPP / C++ / C Code:

if( ((n1==n2)&&(n2!=n3)) || ((n1==n3)&&(n3!=n2)) || ((n2==n3)&&(n3!=n1)) )
  isosceles = true;

crystalattice · #3 24-May-2004, 19:31

Thanks. I knew it was something easy, but I think I was "too close to the problem" to see how to fix it.

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