C语言程序设计(王立柱）第五章答案 结构，联合，枚举

//Date.h
#pragma once
#include<stdio.h>
#include<stdlib.h>
typedef struct {
  int year;
  int month;
  int day;
}Date;
const int NoLeapYear[] = { 31,28,31,30,31,30,31,31,30,31,30,31 };
int LeapYear(int y) {
  return(y % 4 == 0 && y % 100 != 0) || (y % 400) == 0;
}
int DateToNum(Date dt) {
  int i;
  int ndays = 0;
  for (i = 1; i < dt.year; i++)
    ndays += LeapYear(i) ? 366 : 365;
  for (i = 1; i < dt.month; i++)
    ndays += NoLeapYear[i - 1];
  if (dt.month > 2 && LeapYear(dt.year))
    ndays++;
  ndays += dt.day;
  return ndays;
}
Date NumToDate(int ndays) {
  Date dt = { 0,0,0 };
  unsigned n;
  if (ndays <= 0) {
    printf("NumToDate: ndays illegal!\n");
    exit(1);
  }
  dt.year = 1;
  n = 365;
  while (ndays > n) {
    ndays -= n;
    dt.year++;
    n = LeapYear(dt.year) ? 366 : 365;
  }
  dt.month = 1;
  n = 31;
  while (ndays > n) {
    ndays -= n;
    dt.month++;
    n = NoLeapYear[dt.month - 1];
    if (dt.month == 2 && LeapYear(dt.year))
      n++;
  }
  dt.day = ndays;
  return dt;
}
//main.c
#include"Date.h"
#include<stdio.h>
int main() {
  printf("计算一个日期加上和减去一个数字所得到的日期：\n");
  printf("输入一个日期（年，月，日）和一个数字：\n");
  Date dt;
  int num;
  Date temp_d;
  int temp_n;
  scanf_s("%d%d%d%d", &dt.year, &dt.month, &dt.day, &num);
  temp_n = DateToNum(dt) - num;
  temp_d = NumToDate(temp_n);
  printf("减去值的日期：%d年%d月%d日\n", temp_d.year, temp_d.month, temp_d.day);
  temp_n = DateToNum(dt) + num;
  temp_d = NumToDate(temp_n);
  printf("加上值的日期：%d年%d月%d日\n", temp_d.year, temp_d.month, temp_d.day);
  Date dt2 = { 2010,1,1 };
  printf("输入一个日期以判断当天打鱼还是晒网（2011年以后）：");
  Date dt3;
  int temp1, temp2, temp3;
  scanf_s("%d%d%d", &dt3.year, &dt3.month, &dt3.day);
  temp1 = DateToNum(dt2);
  temp2 = DateToNum(dt3);
  temp3 = temp2 - temp1;
  if (temp3 % 5 == 3 || temp3 % 5 == 4)
    printf("晒网");
  else
    printf("打鱼");
  return 0;
}

//main.c
#include<stdio.h>
typedef struct {
  int id;
  double score;
}Student;
int IndexOfMax(const Student* p, int n);
void Selection_s(Student* p, int n);
void SwapByAddress(Student* p, int a, int b);
void OutputArray(const Student* p, int n);
int main() {
  Student s[10];
  int i;
  printf("请输入十个学生的学号（两位数）和平均成绩：\n");
  for (i = 0; i < 10; i++)
    scanf_s("%d%lf", &(s[i].id), &(s[i].score));
  //对于scanf函数，double输入使用%lf,float输入使用%f
  //只有printf才可以使用%f输出double和float，因为有自动类型提升
  Selection_s(s, 10);
  OutputArray(s, 10);
  return 0;
}
int IndexOfMax(const Student* p, int n) {
  int i;
  int max = 0;
  for (i = 1; i < n; i++) {
    if (p[max].score < p[i].score)
      max = i;
  }
  return max;
}
void Selection_s(Student* p, int n) {
  int max;
  while (n > 1) {
    max = IndexOfMax(p, n);
    SwapByAddress(p, max, n - 1);
    n--;
  }
}
void SwapByAddress(Student* p, int a, int b) {
  Student temp;
  temp = p[a];
  p[a] = p[b];
  p[b] = temp;
}
void OutputArray(const Student* p, int n) {
  int i;
  for (i = 0; i < n; i++)
  {
    printf("%d\t%f", p[i].id, p[i].score);
    printf("\n");
  }
}