/*
     Name: Square root calculation
     Author: muguangde
     Date: 09/10/2014-18:40PM
     Description: This is a program to calculate the square root of
     input numbers, binary search method is used, comparing to the
     system owned sqrt function.
*/

#include <iostream>
#include <cmath>
#include <fstream>

using namespace std;

int main()
{
    double num,cand;
    int loopNumber;
    void calSqrt(double,double &,int &);//declare key function
    ofstream outfile;
    outfile.open("output.txt");
    //Prompt the users
    cout<<"Please input the number"<<endl;
    cin>>num;
    while(num>0) {
        calSqrt(num,cand,loopNumber);

        outfile<<"The calculated square root of "<<num<<" is: "<<
               cand<<", after "<<loopNumber<<" iterations."<<endl;

        outfile<<"The build-in function returns the result: "<<sqrt(num)
               <<endl;
        outfile<<"*********************************************"<<endl;

        cout<<"Please input the number"<<endl;
        cin>>num;
    }
    outfile.close();
    return 0;
}

//Function to calculate the sqrt and iteration number
void calSqrt(double num,double &cand,int &loopNumber)
{
    double high=0.0,low=0.0;
    cand=0.0;
    loopNumber=0;


    if(num<1.0) {
        low=num;
        high=1.0;
    } else {
        low=0.0;
        high=num;
    }

    cand=(low+high)/2.0;
    while(fabs(cand*cand-num)>0.000001) {
        if(cand*cand>num)
            high=cand;
        else
            low=cand;
        cand=(low+high)/2.0;
        loopNumber++;
    }

}