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solver.c
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solver.c
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#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <math.h>
double* coefficients;
int n;
double evaluate(double x){
double result = 0;
int i;
for (i = 0; i <= n; i++)
result += coefficients[i] * pow(x, n - i);
return result;
}
double bisection(double a, double b, double tol){
while(1){
double c = (a + b)/2;
double r = evaluate(c);
if (r == 0.0 || (b - a)/2 < tol)
return c;
if ((evaluate(a) > 0) == (r > 0))
a = c;
else
b = c;
}
}
int main(int argc, char** argv){
if (argc <= 1) {
printf("NO FILE PROVIDED\n");
return 0;
}
if (access(*(argv+1), F_OK) != 0){
printf("FILE DOES NOT EXIST\n");
return 0;
}
FILE* f = fopen(argv[1], "r");
double a, b, tol;
fscanf(f, "%d %lf %lf %lf ", &n, &tol, &a, &b);
coefficients = malloc((n+1) * sizeof(double));
int i;
for (i = 0; i <= n; i++)
fscanf(f, "%lf ", &coefficients[i]);
double root = bisection(a, b, tol);
FILE* out = fopen("part2_solver.dat", "w");
fprintf(out, "%lf", root);
fclose(f);
fclose(out);
free(coefficients);
return 0;
}