Analysis of Algorithm for Eating Snakes (2)
James @ www.chenshen.com
The following focuses on several methods in the WORM class: l Public void setdirection (byte direction) This method is used to change the direction of the greedy snake, only 90 degrees. Look at the implementation code below:
IF ((Direction! = CurrentDirection) &&! needupdate) {
// Remove the last element in the list (the head of the snake)
Wormlink SL = (Wormlink) Worm.lastelement ();
INT x = sl.getendx ();
INT Y = sl.getendy ();
// Different movement direction coordinates are different
Switch (direction) {
Case Up: // When this paragraph moves up
IF (CurrentDirection! = DOWN) {
Y--; Needupdate = true;
Break;
Case Down: // When this paragraph moves down
IF (CurrentDirection! = Up) {
Y ; Needupdate = true;
Break;
Case Left: // When this paragraph moves to the left
IF (CurrentDirection! = Right) {
x -; needupdate = true;
Break;
Case Right: // When this paragraph moves to the right
IF (CurrentDirection! = Left) {
x ; Needupdate = true;
Break;
// Need to update when the change direction
IF (NeeduPdate == true) {
Worm.AddeElement (New Wormlink (x, y, 0, direction);
CurrentDirection = Direction;}}
l Public Void Update (Graphics G) This function is updated to eat snake status. Each update increases the head, and the tail is reduced. If it eats the food tail segment, it will not be reduced. It seems like a whole snake.
// increase the greed of the snake head
HEAD = (WORMLINK) WORM.lastelement ();
Head.incadelength ();
// If you don't eat food, the tail is reduced.
IF (! Haseten) {
Wormlink tail;
Tail = (Wormlink) Worm.FirstErayment ();
Int tailx = tail.getx ();
Int taily = tail.gety ();
// If the length of the tail is 0 is 0
Tail.Decreaseledth ();
IF (tail.getlength () == 0) {
Worm.RemoveElement (tail);
// Tail reduction
g.setColor (WormPit.Rase_COLOUR);
Drawlink (G, Tailx, TAILY, TAILX, TAILY, 1);
} else {
// If you eat food, you don't delete the tail.
Haseten = false;
Needupdate = false;
/ / Confirm that it is in the boundary
IF (! Wormpit.isinbounds (Head.Getendx (), Head.Getendy ())) {
// If you don't, you will die the Throw New WormException ("over the Edge");
Headx = (byte) Head.Getendx ();
Heady = (byte) Head.getendy ();
/ / The head of the greedy snake increases
g.setcolor (WormPit.Draw_colour);
Drawlink (G, Headx, Heady, Headx, Heady, 1);
// Judgment whether you eat yourself
For (int i = 0; i SL = (Wormlink) Worm.elementat (i); IF (sl.contains (headx, heady)) { Throw New WormException ("You ATE YourSelf");}} l Void Drawlink (Graphics G, INT X1, INT Y1, INT X2, INT Y2, INT LEN) This function is used to draw a section of the snake, a complete snake is a piece of composite. / / Convert the length into pixel length Len * = Wormpit.cell_size; // (x1 == x2) Description This section is vertical IF (x1 == x2) { / / Turn the X1 into pixel length X1 * = Wormpit.cell_size; / / (Y2 IF (Y2 / / Exchange the head, the left side of the left and transferred into pixels Y1 = Y2 * WORPIT.CELL_SIZE; } else { / / Turn Y1 into pixels Y1 * = Wormpit.cell_size;} G.FillRect (x1, y1, wormpit.cell_size, len); } else { // This is a horizontal section Y1 * = Wormpit.cell_size; IF (x2 / / Exchange the head, the left side of the left and transferred into pixels X1 = x2 * Wormpit.cell_size; } else { X1 * = Wormpit.cell_size;} G.FillRect (x1, y1, len, wormpit.cell_size);} l Public Void Paint (Graphics G) draws a complete greedy snake Wormlink SL; INT X1, X2, Y1, Y2; Int Len; For (int i = 0; i // Take out each paragraph, then draw this, even a complete snake SL = (Wormlink) Worm.elementat (i); X1 = sl.getx (); x2 = sl.getendx (); Y1 = sl.gety (); y2 = sl.getendy (); Len = sl.getlength (); Drawlink (G, X1, Y1, X2, Y2, LEN); About the Author: Shen Yachang, senior programmer, scjp www.chenshen.com jinashen@benq.com August 10, 2003
