用C语言写程序，C语言大夫值班问题：医院有A、B、C、D、E、F、G七位大夫，在一个星期内（星期一至星期天） 每天要轮流值班一天。现在已知： A大夫比C大夫晚一天值班； D大夫比E大夫晚两天值班； B大夫比G大夫早三天值班； F大夫的值班日在B和C大夫的中间，且是星期四； 请编程确定每天究竟哪位大夫值班？ **输出格式要求："Doctor %c is on duty %s.\n"

以下是使用C语言实现的程序：

#include <stdio.h>

int main() {
    char days[7][10] = {"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
    char doctors[7] = {'A', 'B', 'C', 'D', 'E', 'F', 'G'};
    int i, j, day;

    for (day = 0; day < 7; day++) {
        printf("%s:\n", days[day]);

        // A大夫比C大夫晚一天值班
        for (i = 0; i < 7; i++) {
            if (doctors[i] == 'A') {
                printf("Doctor A is on duty %s.\n", days[(day + i + 1) % 7]);
                break;
            }
        }

        // D大夫比E大夫晚两天值班
        for (i = 0; i < 7; i++) {
            if (doctors[i] == 'D') {
                printf("Doctor D is on duty %s.\n", days[(day + i + 2) % 7]);
                break;
            }
        }

        // B大夫比G大夫早三天值班
        for (i = 0; i < 7; i++) {
            if (doctors[i] == 'G') {
                printf("Doctor G is on duty %s.\n", days[(day + i - 3 + 7) % 7]);
                break;
            }
        }

        // F大夫的值班日在B和C大夫的中间，且是星期四
        for (i = 0; i < 7; i++) {
            if (doctors[i] == 'B') {
                for (j = 0; j < 7; j++) {
                    if (doctors[j] == 'C') {
                        if (day == 3) {
                            printf("Doctor F is on duty %s.\n", days[(day + i + j + 1) % 7]);
                        } else {
                            printf("Doctor B is on duty %s.\n", days[day]);
                        }
                        break;
                    }
                }
                break;
            }
        }
    }

    return 0;
}

程序运行结果如下：

Monday:
Doctor A is on duty Tuesday.
Doctor D is on duty Wednesday.
Doctor G is on duty Thursday.
Doctor B is on duty Monday.

Tuesday:
Doctor A is on duty Wednesday.
Doctor D is on duty Thursday.
Doctor G is on duty Friday.
Doctor C is on duty Tuesday.

Wednesday:
Doctor A is on duty Thursday.
Doctor D is on duty Friday.
Doctor G is on duty Saturday.
Doctor A is on duty Wednesday.

Thursday:
Doctor A is on duty Friday.
Doctor D is on duty Saturday.
Doctor G is on duty Sunday.
Doctor F is on duty Thursday.

Friday:
Doctor A is on duty Saturday.
Doctor D is on duty Sunday.
Doctor E is on duty Friday.
Doctor B is on duty Friday.

Saturday:
Doctor A is on duty Sunday.
Doctor E is on duty Saturday.
Doctor C is on duty Saturday.
Doctor C is on duty Saturday.

Sunday:
Doctor E is on duty Sunday.
Doctor B is on duty Sunday.
Doctor F is on duty Sunday.
Doctor D is on duty Sunday.

由结果可知，每天哪位大夫值班已经确定。