CODEWITHSUNDEEP
c
Pheegy
Pheegy

Reputation: 37

Bisection method with recursive approach?

I tried to write a program of bisection method with recursive apporach but it seems not working.

The function is f(x) = ax^2 + bx + c. The parameters in findroot: a b and c are values of a b and c in f(x) p and q indicate the interval (p,q). Assume the input are valid(can always find an answer). Here is my attempt 

int sign(float a, float b,float c,float d)
{
   if (a*d*d + b*d + c > 0) {return 1;}
   if (a*d*d + b*d + c < 0) {return -1;}
   else {return 0;}
}

float find_root(float a, float b, float c, float p, float q)
{
   if (sign(a,b,c,(p+q)/2) == 0){return (p+q)/2;}

   else if (! sign(a,b,c,(p+q)/2) == sign(a,b,c,p))
   {return find_root(a,b,c,p,(p+q)/2);}

   else 
   {return find_root(a,b,c,(p+q)/2,q);}
}

Any correction or advice is appreciated!

Upvotes: 0

Views: 1366

Answers (1)

R Sahu
R Sahu

Reputation: 206567

I have a feeling this line is the problem:

else if (! sign(a,b,c,(p+q)/2) == sign(a,b,c,p))

Perhaps you meant to use:

else if (! (sign(a,b,c,(p+q)/2) == sign(a,b,c,p)))

or

else if ( sign(a,b,c,(p+q)/2) != sign(a,b,c,p) )

Upvotes: 2

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