新概念C语言
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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;
}

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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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