发布的代码没有遵循问题的要求，所以它没有产生预期的输出：

void draw_rectangle(int h, int w) {
    for (int i = 0; i < h; i++) {
        if (i == 0 || i == h - 1) {  // first and last rows

        //         ^^^^^^^^^^^^^        ^^^^^^^^^^^^^^^^^^^

            for (int j = 0; j < w; j++) {
                printf("*");
            }  //      ^^^

        // "The visible characters used in each row must alternate between rows.
        //  The first row will use stars, the second row will use hashtags,
        //  the third row will use stars, and so on."

        // They don't say that the last row must be printed with '*'.

        } else {  // rows in between
            if (i % 2 == 0) {
            //  ^^^^^^^^^^
                printf("#");
            //         ^^^
                for (int j = 0; j < w - 2; j++) {
                    printf(" ");
                }
                printf("#");

            // The second row would the one with index i == 1, so that
            // i % 2 == 1, while the '#' will be printed for the third row.

            } else {
                // [...]
            }
        }
        printf("\n");
    }
}

请注意，打印预期图案的替代算法为

void draw_rectangle(int h, int w) {
    for (int i = 0; i < h; i++) {
        char fill = /* '*' if i % 2 == 0 or '#' otherwise */
        for (int j = 0; j < w; j++) {
            if ( /* (i,j) is on the edges of the rectangle */ )
                putchar(fill); 
            else     
                putchar(' ');
        }
        putchar('\n');
    }
}