```
/* sniper */
/* strategy: since a scan of the entire battlefield can be done in 90 */
/* degrees from a corner, sniper can scan the field quickly. */

/* external variables, that can be used by any function */
int corner;           /* current corner 0, 1, 2, or 2 */
int c1x, c1y;         /* corner 1 x and y */
int c2x, c2y;         /*   "    2 "  "  " */
int c3x, c3y;         /*   "    3 "  "  " */
int c4x, c4y;         /*   "    4 "  "  " */
int s1, s2, s3, s4;   /* starting scan position for corner 1 - 4 */
int sc;               /* current scan start */
int d;                /* last damage check */

/* main */
main()
{
int closest;        /* check for targets in range */
int range;          /* range to target */
int dir;            /* scan direction */

/* initialize the corner info */
/* x and y location of a corner, and starting scan degree */
c1x = 10;  c1y = 10;  s1 = 0;
c2x = 10;  c2y = 990; s2 = 270;
c3x = 990; c3y = 990; s3 = 180;
c4x = 990; c4y = 10;  s4 = 90;
closest = 9999;
new_corner();       /* start at a random corner */
d = damage();       /* get current damage */
dir = sc;           /* starting scan direction */

while (1) {         /* loop is executed forever */

while (dir < sc + 90) {  /* scan through 90 degree range */
range = scan(dir,1);   /* look at a direction */
if (range <= 700 && range > 0) {
while (range > 0) {    /* keep firing while in range */
closest = range;     /* set closest flag */
cannon(dir,range);   /* fire! */
range = scan(dir,1); /* check target again */
if (d + 15 > damage())  /* sustained several hits, */
range = 0;            /* goto new corner */
}
dir -= 10;             /* back up scan, in case */
}

dir += 2;                /* increment scan */
if (d != damage()) {     /* check for damage incurred */
new_corner();          /* we're hit, move now */
d = damage();
dir = sc;
}
}

if (closest == 9999) {       /* check for any targets in range */
new_corner();             /* nothing, move to new corner */
d = damage();
dir = sc;
} else                      /* targets in range, resume */
dir = sc;
closest = 9999;
}

}  /* end of main */

/* new corner function to move to a different corner */
new_corner() {
int x, y;
int angle;
int new;

new = rand(4);           /* pick a random corner */
if (new == corner)       /* but make it different than the */
corner = (new + 1) % 4;/* current corner */
else
corner = new;
if (corner == 0) {       /* set new x,y and scan start */
x = c1x;
y = c1y;
sc = s1;
}
if (corner == 1) {
x = c2x;
y = c2y;
sc = s2;
}
if (corner == 2) {
x = c3x;
y = c3y;
sc = s3;
}
if (corner == 3) {
x = c4x;
y = c4y;
sc = s4;
}

/* find the heading we need to get to the desired corner */
angle = plot_course(x,y);

/* start drive train, full speed */
drive(angle,100);

/* keep traveling until we are within 100 meters */
/* speed is checked in case we run into wall, other robot */
/* not terribly great, since were are doing nothing while moving */

while (distance(loc_x(),loc_y(),x,y) > 100 && speed() > 0)
;

/* cut speed, and creep the rest of the way */

drive(angle,20);
while (distance(loc_x(),loc_y(),x,y) > 10 && speed() > 0)
;

/* stop drive, should coast in the rest of the way */
drive(angle,0);
}  /* end of new_corner */

/* classical pythagorean distance formula */
distance(x1,y1,x2,y2)
int x1;
int y1;
int x2;
int y2;
{
int x, y;

x = x1 - x2;
y = y1 - y2;
d = sqrt((x*x) + (y*y));
return(d);
}

/* plot course function, return degree heading to */
/* reach destination x, y; uses atan() trig function */
plot_course(xx,yy)
int xx, yy;
{
int d;
int x,y;
int scale;
int curx, cury;

scale = 100000;  /* scale for trig functions */
curx = loc_x();  /* get current location */
cury = loc_y();
x = curx - xx;
y = cury - yy;

/* atan only returns -90 to +90, so figure out how to use */
/* the atan() value */

if (x == 0) {      /* x is zero, we either move due north or south */
if (yy > cury)
d = 90;        /* north */
else
d = 270;       /* south */
} else {
if (yy < cury) {
if (xx > curx)
d = 360 + atan((scale * y) / x);  /* south-east, quadrant 4 */
else
d = 180 + atan((scale * y) / x);  /* south-west, quadrant 3 */
} else {
if (xx > curx)
d = atan((scale * y) / x);        /* north-east, quadrant 1 */
else
d = 180 + atan((scale * y) / x);  /* north-west, quadrant 2 */
}
}
return (d);
}


```