6.列出前60個自然數 << Previous Next >> 8.猜數字
7.輸入年份產生日曆

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

// 定義版面大小
int width = 40, year;
int cols, lead, gap;

// 星期幾
const char *wdays[] = { "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa" };

// 每個月有幾天
struct months {
  const char *name;
  int days, start_wday, at;
} months[12] = {
  { "January",  31, 0, 0 },
  { "February", 28, 0, 0 },
  { "March",    31, 0, 0 },
  { "April",    30, 0, 0 },
  { "May",  31, 0, 0 },
  { "June", 30, 0, 0 },
  { "July", 31, 0, 0 },
  { "August",   31, 0, 0 },
  { "September",    30, 0, 0 },
  { "October",  31, 0, 0 },
  { "November", 30, 0, 0 },
  { "December", 31, 0, 0 }
};

// 間距
void space(int n) { while (n-- > 0) putchar(' '); }

// 初始化月份資訊
void init_months()
{
  int i;

  // 判斷閏年
  if ((!(year % 4) && (year % 100)) || !(year % 400))
    months[1].days = 29;

  // 計算每個月份的起始星期幾
  year--;
  months[0].start_wday = (year * 365 + year/4 - year/100 + year/400 + 1) % 7;

  for (i = 1; i < 12; i++)
    months[i].start_wday = (months[i-1].start_wday + months[i-1].days) % 7;

  // 計算列數和間距
  cols = (width + 2) / 22;
  while (12 % cols) cols--;
  gap = cols - 1 ? (width - 20 * cols) / (cols - 1) : 0;
  if (gap > 4) gap = 4;
  lead = (width - (20 + gap) * cols + gap + 1) / 2;
  year++;
}

// 輸出日曆
void print_row(int row)
{
  int c, i, from = row * cols, to = from + cols;

  // 輸出月份
  space(lead);
  for (c = from; c < to; c++) {
    i = strlen(months[c].name);
    space((20 - i)/2);
    printf("%s", months[c].name);
    space(20 - i - (20 - i)/2 + ((c == to - 1) ? 0 : gap));
  }
  putchar('\n');

  // 輸出星期幾
  space(lead);
  for (c = from; c < to; c++) {
    for (i = 0; i < 7; i++)
      printf("%s%s", wdays[i], i == 6 ? "" : " ");
    if (c < to - 1) space(gap);
    else putchar('\n');
  }

  // 輸出日期
  while (1) {
    for (c = from; c < to; c++)
      if (months[c].at < months[c].days) break;
    if (c == to) break;

    space(lead);
    for (c = from; c < to; c++) {
      for (i = 0; i < months[c].start_wday; i++) space(3);
      while(i++ < 7 && months[c].at < months[c].days) {
        printf("%2d", ++months[c].at);
        if (i < 7 || c < to - 1) putchar(' ');
      }
      while (i++ <= 7 && c < to - 1) space(3);
      if (c < to - 1) space(gap - 1);
      months[c].start_wday = 0;
    }
    putchar('\n');
  }
  putchar('\n');
}

// 輸出整年的日曆
void print_year()
{
  int row;
  char buf[32];
  sprintf(buf, "%d", year);
  space((width - strlen(buf)) / 2);
  printf("%s\n\n", buf);
  for (row = 0; row * cols < 12; row++)
    print_row(row);
}

// 檢查年份是否設置
int main(int c, char **v)
{
  int i, year_set = 0;

  // 讀取年份
  printf("Input a valid year: ");
  {
    scanf ("%d", &year);
    for (i = 1; i < c; i++) {
  // 檢查是否有設定寬度參數
   if (!strcmp(v[i], "-w")) {
  if (++i == c || (width = atoi(v[i])) < 20)
          goto bail;
      } else if (!year_set) {
  // 讀取年份參數
   if (!sscanf(v[i], "%d", &year) || year <= 0)
          year = 1969;
        year_set = 1;
      } else
        goto bail;
    }

    init_months();
    print_year();
    return 0;

  bail:
    fprintf(stderr, "bad args\nUsage: %s year [-w width (>= 20)]\n", v[0]);
    exit(1);
  }
}
6.列出前60個自然數 << Previous Next >> 8.猜數字