CODEWITHSUNDEEP
c++
user11495912
user11495912

Reputation: 41

Babylonian square root algorithm output not matching example

I'm doing an assignment and while I have it pretty much entirely done, I've run into a problem. The program is supposed to find the square root of a number the user inputs using the Babylonian square root algorithm. I was given an example output, and mine does not quite match. Also if you see any more issues please, give me a heads up! Especially if it's about the do while loop (it was the only solution I could get that stopped an infinite loop issue I was having).

#include <ios>
#include <iomanip>
#include <iostream>
using namespace std;

int main()
{
    std::cout << std::fixed << std::setprecision(4);

    //variables
    int input;
    double guess, r, check, test;

    //input
    cout << "Enter a number and I will apply the\n";
    cout << "Babylonian square root algorithm until\n";
    cout << "I am within .001 of the correct answer\n";
    cin >> input;

    cout << "You input " << input << "\n";

    //calculate
        guess = input / 2;
        do {
            test = guess;
            r = input / guess;
            guess = (guess + r) / 2;
            cout << "\nguessing " << guess;
        } while (guess != test); //while end

    //check
        check = guess * guess;

    cout << "\nThe Babylons algorithm gives " << guess;
    cout << "\nChecking: " << guess << " * " << guess << " = " << check << "\n";
} //main end

**Example output:** 
 
Enter a number and I will apply the Babylonian square root algorithm 
until I am withing .001 of the correct answer. 
151 
You entered 151 
guessing 38.75 
guessing 21.3234 
guessing 14.2024 
guessing 12.4172 
guessing 12.2889 
The Babylons algorithm gives 12.2889 
Checking: 12.2889 * 12.2889 = 151.016 
Press any key to continue . . .

**My Output:**

Enter a number and I will apply the
Babylonian square root algorithm until
I am within .001 of the correct answer
151
You input 151

guessing 38.5067
guessing 21.2140
guessing 14.1660
guessing 12.4127
guessing 12.2888
guessing 12.2882
guessing 12.2882
guessing 12.2882
The Babylons algorithm gives 12.2882
Checking: 12.2882 * 12.2882 = 151.0000

Upvotes: 1

Views: 124

Answers (1)

user9706
user9706

Reputation:

Change the type of input from int to double:

double input;

which changes initial value of guess = input / 2 from floor(151/2) = 75.0 to 75.5 for the expected sequence of values. Alternatively, cast the enumerator input to a double in the expression with:

guess = (double) input / 2;

or more elegantly via implicit type conversion by using floating point value as the divisor at suggested by @AlanBirtles:

guess = input / 2.0;

To fix the loop test:

#include <math.h>
...
do {
   ...
} while(fabs(test - guest) > 0.001);

Upvotes: 1

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