C-Kurs/Pong/Musterlösung

Musterlösung

#include <stdlib.h>
#include <curses.h>

/* dimensions of the field */
#define WIDTH 40
#define HEIGHT 15
#define PADDLE_HEIGHT 3

/* positions of play things */
int pos_p1_y;
int pos_p2_y;
int pos_ball_x;
int pos_ball_y;
int dir_ball_x;
int dir_ball_y;

/* scores */
int score_p1 = 0;
int score_p2 = 0;

void init() {
	initscr(); /* init for curses */
	noecho();  /* don't display typed chars */
	cbreak();  /* don't buffer terminal lines */
	keypad(stdscr, TRUE);  /* for special keys (e.g. arrow keys) */
	nodelay(stdscr, TRUE); /* don't block in getch() */ 
}

void place_paddles() {
	pos_p1_y = HEIGHT / 2 - PADDLE_HEIGHT / 2;
	pos_p2_y = HEIGHT / 2 - PADDLE_HEIGHT / 2;
}

void place_ball(int dir_x) {
	pos_ball_x = WIDTH / 2;
	pos_ball_y = HEIGHT / 2;
	dir_ball_x = dir_x;
	dir_ball_y = 1;
}

void print_field() {
	clear();
	int x,y;
	
	/* print score */
	printw("         %i                     %i\n", score_p1, score_p2);

	/* print upper frame */
	printw("+");
	for(x=0; x<WIDTH; x++) {
		printw("-");
	}
	printw("+\n");

	for (y=0; y<HEIGHT; y++) {
		/* first column (x==0) is for player1's paddle */
		if (y >= pos_p1_y && y < pos_p1_y+PADDLE_HEIGHT) {
			printw("|#");
		} else if (pos_ball_x == 0 && pos_ball_y == y) {
			printw("|*");
		} else {
			printw("| ");
		}

		/* middle columns (0 < x < WIDTH-1) anywhere the ball can be */
		for (x=1; x<WIDTH-1; x++) {
			if (y == pos_ball_y && x == pos_ball_x) {
				printw("*");
			} else {
				printw(" ");
			}
		}

		/* last column (x==WIDTH-1) is for player2's paddle */
		if (y >= pos_p2_y && y < pos_p2_y+PADDLE_HEIGHT) {
			printw("#|\n");
		} else if (pos_ball_x == WIDTH-1 && pos_ball_y == y) {
			printw("*|\n");
		} else {
			printw(" |\n");
		}
	}

	/* print lower frame */
	printw("+");
	for(x=0; x<WIDTH; x++) {
		printw("-");
	}
	printw("+\n");

	refresh();
}

void key_processing() {
	int ch = getch();
	if (ch == KEY_UP) {
		if (pos_p1_y > 0) {
			pos_p1_y--;
		}
	} else if (ch == KEY_DOWN) {
		if (pos_p1_y < HEIGHT-PADDLE_HEIGHT) {
			pos_p1_y++;
		}
	} else if (ch == 'w') {
		if (pos_p2_y > 0) {
			pos_p2_y--;
		}
	} else if (ch == 's') {
		if (pos_p2_y < HEIGHT-PADDLE_HEIGHT) {
			pos_p2_y++;
		}
	}
}

void detect_collision() {
	/* ball collides with upper/lower bounds */
	if (pos_ball_y <= 0 || pos_ball_y >= HEIGHT-1) {
		dir_ball_y *= -1;
	}

	/* ball collides with player1's paddle */
	if (pos_ball_x == 1 && pos_ball_y >= pos_p1_y && pos_ball_y < pos_p1_y + PADDLE_HEIGHT) {
		dir_ball_x *= -1;
	}

	/* ball collides with player2's paddle */
	if (pos_ball_x == WIDTH-2 && pos_ball_y >= pos_p2_y && pos_ball_y < pos_p2_y + PADDLE_HEIGHT) {
		dir_ball_x *= -1;
	}
}

void move_ball() {
	pos_ball_x += dir_ball_x;
	pos_ball_y += dir_ball_y;
}

int detect_ball_out() {
	/* ball is out on left side -> point for player2 */
	if (pos_ball_x <= 0) {
		return 2;
	}

	/* ball is out on right side -> point for player1 */
	if (pos_ball_x >= WIDTH-1) {
		return 1;
	}

	return 0;
}

int play_round() {
	int ball_out;
	int count = 0;
	while( !(ball_out = detect_ball_out()) ) {
		key_processing();
		if(count == 0) {
			move_ball();
			detect_collision();
		}
		print_field();
		count = (count + 1) % 5;
		usleep(20000);
	}
	return ball_out;
}

int main() {
	init();
	place_paddles();
	place_ball(1);

	while(score_p1 < 10 && score_p2 < 10) {
		int round_won = play_round();
		if (round_won == 1) {
			score_p1++;
			place_ball(1);
		} else if (round_won == 2) {
			score_p2++;
			place_ball(-1);
		}
		sleep(1);
		flushinp(); /* keys could've been pressed during sleep ->  emty the input buffer */
	}

	if (score_p1 > score_p2) {
		printw("Player 1 wins!\n");
	} else {
		printw("Player 2 wins!\n");
	}
	refresh();
	sleep(3);

	endwin();
}

Musterlösung KI

Einen halbwegs ausgeglichenen Gegner bringt die folgende Lösung. Die Funktion ai_opponent muss dazu in der Schleife von play_round am besten nach key_processing aufgerufen werden.

int can_move() {
	if (dir_ball_x < 0) { /* we don't want to move when the ball departs from us */
		return 0;
	}
	int rnd = rand();
	if (pos_ball_x <= WIDTH / 4) {
		rnd &= 0x1f; /* zero with probability 1/32 */
	} else if (pos_ball_x <= WIDTH / 2) {
		rnd &= 0x0f; /* zero with probability 1/16 */
	} else if (pos_ball_x <= WIDTH * 3 / 4) {
		rnd &= 0x07; /* zero with probability 1/8 */
	} else {
		rnd &= 0x03; /* zero with probability 1/4 */
	}
	return !rnd;
}

void ai_opponent() {
	if (can_move()) {
		int middle_pad_pos = pos_p2_y + 1;
		if (pos_ball_y < middle_pad_pos) {
			if (pos_p2_y > 0) {
				pos_p2_y--;
			}
		} else if (pos_ball_y > middle_pad_pos) {
			if (pos_p2_y < HEIGHT - PADDLE_HEIGHT) {
				pos_p2_y++;
			}
		}
	}
}

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