编程环境Visual Studio 2017
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#include <iostream> #include <string> #include <cctype> using namespace std; // practice 1 void p7_1(void) { double x, y; double avg = 0; cout << "Enter two numbers: "; cin >> x >> y; while (x != 0 && y != 0) { avg = 2.0 * x * y / (x + y); cout << "The average of " << x << " and " << y << " is " << avg << endl; cout << "Enter the next two numbers: "; cin >> x >> y; } } // practice 2 void GetInput(double *grade, unsigned int *number) { cout << "You can enter up to 10 grades( -1 to quit): " << endl; while (cin >> grade[(*number)++]) { if (grade[*number - 1] == -1) { break; } } (*number)--; } void PrintArray(const double *grage, const unsigned int number) { cout << "The grade is: " << endl; for (unsigned int i = 0; i < number; i++) { cout << grage[i] << " "; } cout << endl; } void CalAvg(const double *grade, const unsigned int number) { double total = 0.0; cout << "The average is :"; for (unsigned int i = 0; i < number; i++) { total += grade[i]; } cout << total / number << endl; } void p7_2(void) { double grade[10]; unsigned int enter = 0; GetInput(grade, &enter); PrintArray(grade, enter); CalAvg(grade, enter); return; } // practice 3 struct box { char maker[40]; float height; float width; float length; float volume; }; void PrintBox(struct box mbox) { cout << "Box maker: " << mbox.maker << endl; cout << "Box height: " << mbox.height << endl; cout << "Box width: " << mbox.width << endl; cout << "Box length: " << mbox.length << endl; cout << "Box volume: " << mbox.volume << endl; } void CalBoxVolume(struct box *pbox) { pbox->volume = pbox->height * pbox->width * pbox->length; } void p7_3(void) { struct box mbox = { "Jimmy Chen", 0.25, 4.0, 1.0, 0.0 }; PrintBox(mbox); CalBoxVolume(&mbox); PrintBox(mbox); } // practice 4 long double probability(unsigned number, unsigned picks) { long double result = 1.0; long double n = 0; unsigned p; for (n = number, p = picks; p > 0; n--, p--) { result = result * n / p; } return result; } void p7_4(void) { unsigned field1 = 47; unsigned field2 = 27; cout << "You have on chance in "; cout << probability(47, 5) * probability(27, 1); cout << " of winning.\n" << endl; } // practice 5 long long factorial(unsigned int number) { if (number == 0 || number == 1) { return 1; } else { return number * factorial(number - 1); } } void p7_5(void) { long long result = 0; unsigned int input = 0; cout << "Please enter the number: "; cin >> input; while (1) { result = factorial(input); cout << "The result of " << input << "! is " << result << "." << endl; cout << "Please enter the next number: "; cin >> input; } } // practice 6 unsigned int Fill_array(double double_array[], unsigned int length) { unsigned int n_input = 0; cout << "Enter double numbers (non-digital to quit): " << endl; for (size_t i = 0; i < length; i++) { if (cin >> double_array[i]) { n_input++; } else { break; } } return n_input; } void Show_array(double double_array[], unsigned int length) { cout << "The double array is :" << endl; for (size_t i = 0; i < length; i++) { cout << double_array[i] << " "; if ((i + 1) % 5 == 0) { cout << endl; } } if (length % 5 != 0) { cout << endl; } } void Reverse_array(double double_array[], unsigned int length) { cout << "Revert the array" << endl; for (size_t i = 0; i < length / 2; i++) { double tmp = double_array[i]; double_array[i] = double_array[length - 1 - i]; double_array[length - 1 - i] = tmp; } } void p7_6(void) { double double_array[10]; unsigned int n_input; n_input = Fill_array(double_array, 10); Show_array(double_array, n_input); Reverse_array(double_array, n_input); Show_array(double_array, n_input); } // practice 7 int fill_array(double *ar_begin, double *ar_end) { double temp = 0.0; int i = 0; double *ar_tmp = nullptr; for (ar_tmp = ar_begin; ar_tmp < ar_end; ar_tmp++) { cout << "Enter value #" << (i + 1) << ": "; cin >> temp; if (!cin) { cin.clear(); while (cin.get() != '\n') continue; cout << "Bad input; input preocess terminated.\n"; break; } else if (temp < 0) { break; } *ar_tmp = temp; i++; } return i; } void show_array(const double *ar_begin, const double *ar_end) { const double *ar_tmp = nullptr; unsigned int i = 0; for (ar_tmp = ar_begin; ar_tmp < ar_end; ar_tmp++) { cout << "Property #" << (i + 1) << ": $"; cout << *ar_tmp << endl; i++; } } void revalue(double *ar_begin, double *ar_end, double r) { for (double * ar = ar_begin; ar < ar_end; ar++) { *ar *= r; } } void p7_7(void) { double properties[10]; int size = fill_array(properties, properties + 10); show_array(properties, properties + size); if (size > 0) { cout << "Enter revaluation factor: "; double factor; while (!(cin >> factor)) { cin.clear(); while (cin.get() != '\n') continue; cout << "Bad input; Please enter a number: "; } revalue(properties, properties + size, factor); show_array(properties, properties + size); } cout << "Done.\n"; return; } // practice 8 const int Seasons = 4; const char *Snames[Seasons] = { "Spring", "Summer", "Fall", "Winter" }; struct cost { double expenses[Seasons]; }; void fill(double *pa) { for (int i = 0; i < Seasons; i++) { cout << "Enter " << Snames[i] << " expenses: "; cin >> pa[i]; } } void show(double *pa) { double total = 0.0; cout << "\nEXPENSES\n"; for (int i = 0; i < Seasons; i++) { cout << Snames[i] << ": $" << pa[i] << endl; total += pa[i]; } cout << "Total Expenses: $" << total << endl; } void fill(struct cost *pCost) { for (int i = 0; i < Seasons; i++) { cout << "Enter " << Snames[i] << " expenses: "; cin >> pCost->expenses[i]; } } void show(struct cost *pCost) { double total = 0.0; cout << "\nEXPENSE\n"; for (int i = 0; i < Seasons; i++) { cout << Snames[i] << ": $" << pCost->expenses[i] << endl; total += pCost->expenses[i]; } cout << "Total Expense: $" << total << endl; } void p7_8(void) { // situation a cout << "Situation a: " << endl; double pa[Seasons] = { 0 }; fill(pa); show(pa); // situation b cout << endl << endl; cout << "Situation b: " << endl; struct cost *pCost = new struct cost; fill(pCost); show(pCost); delete pCost; } // practice 9 const int SLEN = 30; struct student { char fullname[SLEN]; char hobby[SLEN]; int ooplevel; }; int getinfo(student pa[], int n) { int enter = 0; for (int i = 0; i < n; i++) { cout << "Enter the infomation of student #" << i+1 << endl; cout << "Enter full name (blank line to quit): "; cin.getline(pa[i].fullname, SLEN); cout << "Enter hobby: "; cin.getline(pa[i].hobby, SLEN); cout << "Enter ooplevel: "; cin >> pa[i].ooplevel; while (cin.get() != '\n') continue; enter++; } return enter; } void display1(student st) { cout << "Using display1(student st): " << endl; cout << "Full name: " << st.fullname << endl; cout << "Hobby: " << st.hobby << endl; cout << "Ooplevel: " << st.ooplevel << endl; } void display2(const student *st) { cout << "Using display2(const student *st)" << endl; cout << "Full name: " << st->fullname << endl; cout << "Hobby: " << st->hobby << endl; cout << "Ooplevel: " << st->ooplevel << endl; } void display3(const student pa[], int n) { cout << "Using display3(const student pa[], int n)" << endl;; for (int i = 0; i < n; i++) { cout << "Infomation of student #" << i + 1 << ": " << endl; cout << "Full name: " << pa[i].fullname << endl; cout << "Hobby: " << pa[i].hobby << endl; cout << "Ooplevel: " << pa[i].ooplevel << endl; } } void p7_9(void) { cout << "Enter class size: "; int class_size; cin >> class_size; while (cin.get() != '\n') continue; student *ptr_stu = new student[class_size]; int entered = getinfo(ptr_stu, class_size); for (int i = 0; i < entered; i++) { display1(ptr_stu[i]); display2(&ptr_stu[i]); } display3(ptr_stu, entered); delete[] ptr_stu; cout << "Done.\n"; return; } // practice 10 double add(double x, double y) { return x + y; } double mul(double x, double y) { return x * y; } double calculate(double x, double y, double(*fun)(double, double)) { return fun(x, y); } void p7_10(void) { double x = 0.0; double y = 0.0; cout << "Enter two double number: "; while (cin >> x >> y) { cout << "Call add, the result of " << x << " and " << y << " is " << calculate(x, y, add) << endl; cout << "Call mul, the result of " << x << " abd " << y << " is " << calculate(x, y, mul) << endl; cout << "Enter next two double number: "; } } int main(int argc, char **argv) { p7_10(); while (getchar()); return 0; } |
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第二题练习input那里改成这样更好吧
while (cin >> grade[(*number)++], *number < 10)
{
if (grade[*number - 1] == -1)
{
(*number)--;
break;
}
好像比较少看到有这种用法啊。另外这里提出问题与你探究下：在while的条件判断语句里面使用逗号表达式，貌似是以最后一个逗号表达式的值作为while判断语句的值吧，那如果cin执行输入有误的话，用逗号表达式的while判断好像没有办法判断出来吧！
啊，我是自己刚开始看书自学的，后来研究了一下while那样用好像是不好，下面是我自己写的第二题代码，感觉bug会少点
#include
using namespace std;
void input( double *x ,int &enter);
void show(double *x, int enter);
void avg(double *x, int enter);
int main()
{
double grade[10];
int enter;
input(grade,enter);
show(grade, enter);
avg(grade, enter);
return 0;
}
void input(double *x, int &enter)
{
cout << "你可以最多输入10个成绩，输入-1提前结束" << endl;
for (enter = 0; enter > x[enter];
if (x[enter] ==(-1))
break;
}
return;
}
void show(double *x, int enter)
{
for (int i = 0; i < enter; i++)
{
cout << x[i] << " ";
}
return;
}
void avg(double *x, int enter)
{
double sum, avg;
for (int i = 0; i < enter; i++)
{
sum += x[i];
}
avg = sum / enter;
cout << endl << "平均成绩是" << avg << endl;
return;
}
自学中，谢谢楼主大大的答案参考。
第二题输入数组数据的修改，楼主大大可以看下。
void input(int arr[],int *n)
{
for (int i = 0; i < 10; i++)
{
cout << "input grade" << i+1 <> arr[i];
if (arr[i] == -1)
{
(*n) = i;
break;
}
}
}
7-7fill_array函数要求返回值是一个指向结尾的指针不是数字