Distance between two points without using the square root

Raphm picture Raphm · May 3, 2013 · Viewed 11.6k times · Source

Is it possible to calculate the distance between two points without having to use the math.h library? I know that, using the math.h library, it would have to be something among these lines (Euclidean distance formula):

int Distance(int x1, int y1, int x2, int y2)

    {
    int dx = x2 - x1;
    int dy = y2 - y1;
    return sqrt(dx*dx + dy*dy);
    }

However, is there a way of doing this exact same thing but without using the square root (which needs the math.h library)?

EDIT: Whenever I try the following code, it gives me Floating Point Exception (Core Dumped):

float sqrt(int x) {
        int i;
        float s;
        s=((x/2)+x/(x/2)) / 2; /*first guess*/
        for(i=1;i<=4;i++) { /*average of guesses*/
            s=(s+x/s)/2;
        }
        return s;
    }

float Distance(float x1, float y1, float x2, float y2) {
    float dx = x2 - x1;
    float dy = y2 - y1;
    return sqrt(dx*dx + dy*dy);
}

int main() {
  printf("%f", Distance(1, 2, 2, 1));
  return 0;
}

Answer

BLUEPIXY picture BLUEPIXY · May 3, 2013
int int_sqrt(int x){
    int s, t;

    s = 1;  t = x;
    while (s < t) {
        s <<= 1;
        t >>= 1;
    }//decide the value of the first tentative

    do {
        t = s;
        s = (x / s + s) >> 1;//x1=(N / x0 + x0)/2 : recurrence formula
    } while (s < t);

    return t;
}