Lesson-14.md

December 7, 2012 · View on GitHub

Lesson 14 Is there a way out? 判断地图上某点是否有出路

#include <stdio.h>
#include <time.h>
#include <stdlib.h> 

/* define chessboard size */
#define ROW  10
#define COL  10

/* define chessboard using matrix */
int chessboard[ROW][COL] = { {0} };

void init(int board[ROW][COL])
{
	int i, j;
	
	srand(time(NULL));
	
	for (i = 0; i < ROW; i++) 	
		for (j = 0; j < COL; j++) 		
			board[i][j] = rand() % 2;
			
	return;
}

/* display chessboard using printf */
void print(int board[ROW][COL])
{
	int i, j;

	printf("\n");
	printf("  ");

	for (j = 0; j < COL; j++)
		printf(" %d", j);
	printf("\n");

	printf(" -");
	for (j = 0; j < COL; j++)
		printf(" -");

	printf("\n");
	for (i = 0; i < ROW; i++) {
		printf("%d| ", i);
		for (j = 0; j < COL; j++) {
			printf("%d ", board[i][j]);
		}
		printf("\n");
	}

	printf("\n");
}

/* test (x, y) is valid before put chess */
int onboard(int x, int y)
{
	if (x >= ROW || x < 0)
		return 0;

	if (y >= COL || y < 0)
		return 0;

	return 1;
}

int check(int x, int y)
{
	int i = 0;
	int counter = 1;	
	int nx, ny;		// next x y

	// up, down, left, right, 
	int dirx[4] = { -1, 1, 0, 0 };
	int diry[4] = { 0, 0, -1, 1 };

	counter = 0;
	
	// 4 directions
	for (i = 0; i < 4; i++)
	{
		nx = x;
		ny = y;
		
		nx += dirx[i];
		ny += diry[i];
		
		// if (nx, ny) is out of board, then continue;
		if (!onboard(nx, ny))
			continue;
		
		if (chessboard[nx][ny] == 0)
		{
			counter++;
			printf("there is %d direction (%d, %d) out!\n", counter, dirx[i], diry[i]);
		}
	}

	return counter;
}

int main(int argc, char *argv[])
{
	int x = 4, y = 4;
	int ways = 0;
	
	print(chessboard);
	init(chessboard);	
	print(chessboard);

	printf("please input a point position: ");
	scanf("%d %d", &x, &y);
	printf("point(%d, %d)\n", x, y);
	
	ways = check(x, y);
	printf("Total is %d way out!\n", ways);
	
	return 0;
}

知识点

  • 二维数组 a[][]
  • 随机函数 rand()

课堂讨论

  • dirx 和 diry 的数组在代码易读性上是否还有改进的空间？
  • 如果在方向判断上，要加上左上，左下，右上，右下这4个方向，如何修改？

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