Bresenham

#include <graphics.h>
#define DELAY 10
int color = RED;

void lineBresenham(int x1, int y1, int x2, int y2)  // Ve duong thang Bresenham hoc tren truong
{
    int x, y, Dx, Dy, p, c1, c2;
    Dx = abs(x2 - x1);
    Dy = abs(y2 - y1);
    p = 2*Dy - Dx;
    c1 = 2*Dy;
    c2 = 2*(Dy-Dx);
    x = x1;
    y = y1;

    int x_unit = 1, y_unit = 1;

    if (x2 - x1 < 0)
        x_unit = -x_unit;
    if (y2 - y1 < 0)
        y_unit = -y_unit;

    putpixel(x,y,color);
    while(x != x2){
        delay(DELAY);
        if (p<0) p += c1;
        else{
            p += c2;
            y += y_unit;
        }
        x += x_unit;
        putpixel(x,y,color);
    }
}


void lineBresenham_1(int x1, int y1, int x2, int y2) // Ve duong thang Bresenham wiki
{
    int c2, c, Dx, Dy, x, y;
    Dx = abs(x2 - x1);
    Dy = abs(y2 - y1);
    c = Dx - Dy;
    c2 = 2*c;
    x = x1;
    y = y1;

    int x_unit = 1, y_unit = 1;

    if (x2 - x1 < 0)
        x_unit = -x_unit;
    if (y2 - y1 < 0)
        y_unit = -y_unit;

    while(x != x2)
    {
        delay(DELAY);
        putpixel(x, y, color+1);
        if (x1 == x2 && y1 == y2) return;
        c2 =2*c;
        if (c2 > -Dy)
        {
            c = c - Dy;
            x = x + x_unit;
        }
        if (c2 < Dx)
        {
            c = c + Dx;
            y = y + y_unit;
        }
    }
}
int main(){
    int gd,gm=VGAMAX; gd=DETECT;
    initgraph(&gd,&gm,NULL);
    lineBresenham(200,150, 150, 50);        // ve duong thang
    lineBresenham(200,150, 150, 400);
    lineBresenham(200,150, 250, 400);
    lineBresenham(200,150, 250, 10);

    lineBresenham_1(200,150, 150, 50);      // ve duong thang
    lineBresenham_1(200,150, 150, 400);
    lineBresenham_1(200,150, 250, 400);
    lineBresenham_1(200,150, 250, 10);

    outtextxy(250, 400, "YES");
    outtextxy(250, 10, "YES");
    outtextxy(150, 400, "YES");
    outtextxy(150, 50, "YES");

    getchar();
    return 0;
}