#include<stdio.h>
#include<stdlib.h>
#include <math.h>

float horner(float *p, int n, float x);
float bisection(float *p, int n, float a, float b);

float horner(float *p, int n, float x)
{
/*
   float result = 0.0;
for (int i=0; i<n; i++) {
        result = result*x + p[i];
}

return result;
*/
// pointer implementation
float holder;
holder = 0.0;
for (int i = 0;i < n;i++){
holder = holder * x + *(p + i);
}
return holder;
}

//your bisection method implementation
float bisection(float *p, int n, float a, float b)
{
float result;
float tolerance = 1e-6;
float c = 0.0;

if ( horner(p,n,a) * horner(p,n,b) < 0.0){

while ( b - a >= tolerance){

c = (a+b)/2.0;

if (horner(p,n,c) == 0.0){
result = c;
break;
}

else if ( horner(p,n,c) * horner(p,n,a) < 0.0 ){
b = c;
}
else {

a = c;
}
}

if ( b - a < tolerance){
result = c;
}

}

return result;


}