題目要求:
用C編寫程序并注釋
N*N矩陣輸出
N=3時輸出
1 2 3
  8 9 4
  7 6 5
N＝4時輸出
   1  2  3   4
   12 13 14  5
   11 16 15  6
   10  9  8  7

編寫當N時的輸出

代碼:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum {
        MASK_UP                = 1,
        MASK_DOWN        = 2,
        MASK_LEFT        = 4,
        MASK_RIGHT        = 8,
       
        TURN_NONE        = 0,
        TURN_UP                = 1,
        TURN_DOWN        = 2,
        TURN_LEFT        = 3,
        TURN_RIGHT        = 4,
};

int directs[5][2] = {
        {0, 0},                // 0:TURN_NONE
        {-1, 0},        // 1:TURN_UP
        {1, 0},                // 2:TURN_DOWN
        {0, -1},        // 3:TURN_LEFT
        {0, 1},                // 4:TURN_RIGHT
};

int rules[16] = {
        TURN_NONE,        // 0:none
        TURN_UP,        // 1:up
        TURN_DOWN,        // 2:down
        TURN_NONE,        // 3:invalid
        TURN_LEFT,        // 4:left
        TURN_LEFT,        // 5:left and up
        TURN_DOWN,        // 6:left and down
        TURN_NONE,        // 7:invalid
        TURN_RIGHT,        // 8:right
        TURN_UP,        // 9:right and up
        TURN_RIGHT,        // 10:right and down
        TURN_NONE,        // 11-15:invalid
};
int next_pos(int *matrix, int n, int i, int j, int *nexti, int *nextj)
{
        if (i == -1 || j == -1)
        {
                *nexti = 0;
                *nextj = 0;
                return 1;
        }
        int mask = 0;
        if (i - 1 >= 0 && matrix[(i - 1) * n + j] == 0)                // up ok
                mask |= MASK_UP;
        if (i + 1 <= n - 1 && matrix[(i + 1) * n + j] == 0)        // down ok
                mask |= MASK_DOWN;
        if (j - 1 >= 0 && matrix[i * n + (j - 1)] == 0)                // left ok
                mask |= MASK_LEFT;
        if (j + 1 <= n - 1 && matrix[i * n + (j + 1)] == 0)        // right ok
                mask |= MASK_RIGHT;
       
        int rule = rules[mask];
        int *direct = directs[rule];
        if (direct[0] == 0 && direct[1] == 0)
                return 0;
        *nexti = i + direct[0];
        *nextj = j + direct[1];
        return 1;
}

int main(int argc, char *argv[])
{
        if (argc != 2)
                return -1;
        int n = atoi(argv[1]);
        if (n <= 0)
                return -1;
       
        int *matrix = (int*)malloc(n * n * sizeof(int));
        memset(matrix, 0, n * n * sizeof(int));

        int i = -1;
        int j = -1;
        int value = 1;
        while (next_pos(matrix, n, i, j, &i, &j) != 0)
        {
                matrix[i * n + j] = value++;
        }

        for (i = 0; i < n; i++)
        {
                for (j = 0; j < n; j++)
                {
                        printf("%d", matrix[i * n + j]);
                        if (j != n - 1)
                                printf("\t");
                }
                printf("\n");
        }
       
        free(matrix);
        return 0;
}