Bisection.c

// Bisection method with maximum iteration
// Lab Class No 1
#include<stdio.h>

double my_function(double x) //returns the value of x
{
    double fx=(x*x)-x-1;
    return fx;
}

double bisection(double a, double b, double tolerance, int max_iter)
{
    double prev_root,x,ans;
    int i;
    for(i=1;i<max_iter;i++)
    {
        x=(a+b)/2.00;
        ans=my_function(x);
        if(my_function(a)<0 && ans<0) //if both of these are negative
                                      //then update the negative one
        {
            a=x;
        }
        else
            b=x;
    }
    return x;
}
int main()
{
    // f(x0=x^2-x-1;
    float a,b,x,tolerance,root;
    int max_iter;
    // Enter the range [a,b], tolerance and maximum iteration
    scanf("%lf %lf %lf %d", &a, &b, &tolerance, &max_iter);

    if(my_function(a)*my_function(b)>0) // Check the range
        printf("Invalid Range\n");
    else
    {
        root=bisection(a,b,tolerance,max_iter);
        printf("%lf\n",root);
    }
}

/*
Input:
2 3
0.001
100
Output:
2.125000
*/