C++ Primer Plus 第五章答案 循环和关系表达式

//5.8
//1
输入条件循环在进入输入循环体之前评估测试表达式。如果条件最初为flase，则循
退出条件循环在处理循环体之后评估测试表达式，即使条件最初为flase，循环也会
for和while都是输入条件循环，do while是退出条件循环。
//2
将打印：
01234
//3
将打印：
0369
12
//4
将打印：
6
8
//5
将打印：
k = 8
//6
使用 *= 运算符最简单：
for (int num = 1; num <= 64; num *= 2)
cout << num << " ";
//7
将语句放在一个大括号中将形成一个复合语句或代码块。
//8
第一个语句将20赋给x，第二个语句将1赋给y
//9
cin>>ch将跳过空格，换行符，和制表符，其他两种格式将读取这些字符。

//第五章编程练习
#include<iostream>
#include<array>
#include<string>
#include<cstring>
using namespace std;
//practice 1
void p5_1()
{
  int a = 0;
  int b = 0;
  cout << "Enter two number to add all number between them:please enter the smaller one first:\n";
  cin >> a;
  cin >> b;
  int sum=0;
  for (a; a < b + 1; a++)
    sum += a;
  cout<<"The sum of them is: "<<sum<<endl;
}
//practice 2
const int Arsize = 101;
void p5_2()
{
  array<long double, Arsize>arr = {};
  arr[1] = arr[0] = 1.0;
  for (int i = 2; i < Arsize; i++)
    arr[i] = i * arr[i - 1];
  for (int i = 0; i < Arsize; i++)
    cout << i << "!=" << arr[i] << endl;
}
//practice 3
void p5_3()
{
  int num = 0;
  int sum = 0;
  while(1)
  {
    cout << "Enter a number (0 to exit):";
    cin >> num;
    if (num == 0)
      break;
    sum += num;
    cout << "Untill now,the sum of the number you inputed is: " << sum << endl;
  }
  cout << "Done!\n";
}
//practice 4
void p5_4()
{
  int investment = 100;
  double profit1 = 110;
  double profit2 = 105;
  int i;
  for(i=1;profit2<=profit1;i++)
  {
    profit1 += 10;
    profit2 += (profit2 * 0.05);
  }
  cout << "复利投资收入高于单利在第n年，n=" << i << endl;
  cout << "此时复利收入为" << profit2 << ",单利收入为" << profit1 << endl;
}
//practice 5
void p5_5()
{
  string month[12] = { "January", "February", "March", "April", "May", "June", 
    "July", "August", "Septempber", "October", "November", "December" };
  int sell[12] = {};
  int sum=0;
  for (int i=0;i<12;i++)
  {
    cout << month[i] << ": ";
    cin >> sell[i];
    sum += sell[i];
  }
  cout << "全年总销售量是：" << sum << endl;
}
//practice 6
void p5_6()
{
  string month[12] = { "January", "February", "March", "April", "May", "June",
    "July", "August", "Septempber", "October", "November", "December" };
  int sell[3][12];
  int sum[3] = {};
  int i, j;
  for (i = 0; i < 3; i++)
  {
    cout << "The sell on " << i+1 << " year:\n";
    for (j = 0; j < 12; j++)
    {
      cout << month[j] << ": ";
      cin >> sell[i][j];
      sum[i] += sell[i][j];
    }
    cout << "The sum on " << i + 1 << " year: " << sum[i] << endl;
  }
  cout << "三年销售总量：" << sum[0] + sum[1] + sum[2] << endl;
}
//practice 7
void p5_7()
{
  struct car 
  {
    string company;
    int time=0;
  };
  int num = 1;
  cout << "How many cars do you wish to catalog? ";
  (cin >> num).get();
  car * pc=new car[num];
  for(int i=0;i<num;i++)
  {
    cout << "Car #" << i + 1 << ":\n";
    cout << "Please enter the company: ";
    getline(cin,pc[i].company);
    cout << "Please enter the year made: ";
    (cin >> pc[i].time).get();
  }
  cout << "Here is your collection: \n";
  for(int i=0;i<num;i++)
    cout << pc[i].time << " " << pc[i].company << endl;
}
//practice 8
void p5_8()
{
  char word[20];
  unsigned int num_word = 0;
  cout << "Enter words(to stop,type the word done): " << endl;
  while (cin >> word)
    if (strcmp(word, "done"))
      num_word++;
    else break;
  cout << "You entered a total  of " << num_word << " words.";
}
//practice 9
void p5_9()
{
  string word;
  unsigned n_word = 0;
  cout << "Enter words(to stop,type the word done): " << endl;
  while (cin >> word)
    if (word!="done")
      n_word++;
    else break;
  cout << "You entered a total  of " << n_word << " words.";
}
//practice 10
void p5_10()
{
  int num = 0;
  cout << "Enter number of rows: ";
  cin >> num;
  for (int i = 1; i <= num; i++)
  {
    for (int j = num - i; j > 0; j--)
      cout << ".";
    for (int m = i; m > 0; m--)
      cout << "*";
    cout << endl;
  }
}
int main()
{
  p5_10();
  return 0;
}