我的程序是一个成绩计算器，如果您输入P，M或D，程序将根据您的要求添加点数。我想警告用户这些是您可以使用的唯一字符串。以下是该计划的代码：
#include <cstdlib>
#include <iostream>
#include <string>
using namespace std;
int points = 0;
string lesson[18];
char grades[18];
void start();
void lessons();
void grades_selector();
void award_points();
void point();
void BTEC();
void UCAS();
int main(int argc, char *argv[])
{
start();
lessons();
grades_selector();
point();
cout << "You have achieved " << points << " points." << endl;
BTEC();
UCAS();
system("PAUSE");
return EXIT_SUCCESS;
}
void start()
{
cout << "BTEC & UCAS GRADE CALCULATOR." << endl;
cout << "For every lesson input either (P)ass, (M)erit, (D)istinction." << endl;
}
void lessons()
{
lesson[0] = "Year 1:Communication and Employability Skills";
lesson[1] = "Year 1:Computer Systems";
lesson[2] = "Year 1:Information Systems";
lesson[3] = "Year 1:Event Driven Programming";
lesson[4] = "Year 1:Database Design";
lesson[5] = "Year 1:Data Analysis and Design";
lesson[6] = "Year 1:Installing and upgrading Software";
lesson[7] = "Year 1:Digital Graphics for Interactive Media";
lesson[8] = "Year 1:CCNA Network Home Small Business";
lesson[9] = "Year 2:Software Design and Development";
lesson[10] = "Year 2:Object Oriented Programming";
lesson[11] = "Year 2:Procedural Programming";
lesson[12] = "Year 2:Client Side Customisation of Web Pages";
lesson[13] = "Year 2:Developing Computer Games";
lesson[14] = "Year 2:Human Computer Interaction";
lesson[15] = "Year 2:Computer Animation";
lesson[16] = "Year 2:Computer Games Platforms and technologies";
lesson[17] = "Year 2:3D Modelling";
}
void grades_selector()
{
int index; //local variable
for (index = 0; index < 18; index = index + 1)
{
cout << "What grade was achieved for " << lesson[index] << "?" << endl;
cin >> grades[index];
} }
void point()
{
int index;
for (index = 0; index < 18; index = index + 1)
{
switch ( grades[index] )
{
case 'D':
points = points + 90;
break;
case 'd':
points = points + 90;
break;
case 'M':
points = points + 80;
break;
case 'm':
points = points + 80;
break;
case 'P':
points = points + 70;
break;
case 'p':
points = points + 70;
break;
default:
points = 0;
break;
}
}
}
void BTEC()
{
if( points >= 1590)
{
cout <<" You have achieved D*D*D*" << endl;
}
else if( points >= 1560)
{
cout <<" You have achieved D*D*D" << endl;
}
else if( points >= 1530)
{
cout <<" You have achieved D*DD" << endl;
}
else if( points >= 1500)
{
cout <<" You have achieved DDD" << endl;
}
else if( points >= 1460)
{
cout <<" You have achieved DDM" << endl;
}
else if( points >= 1420)
{
cout <<" You have achieved DMM" << endl;
}
else if( points >= 1380)
{
cout <<" You have achieved MMM" << endl;
}
else if( points >= 1340)
{
cout <<" You have achieved PMM" << endl;
}
else if( points >= 1300)
{
cout <<" You have achieved PPM" << endl;
}
else
{
cout <<" You have achieved PPP" << endl;
}
}
void UCAS()
{
if( points >= 1590)
{
cout <<" You have 420 UCAS points." << endl;
}
else if( points >= 1560)
{
cout <<" You have 400 UCAS points." << endl;
}
else if( points >= 1530)
{
cout <<" You have 380 UCAS points" << endl;
}
else if( points >= 1500)
{
cout <<" You have 360 UCAS points." << endl;
}
else if( points >= 1460)
{
cout <<" You have 320 UCAS points." << endl;
}
else if( points >= 1420)
{
cout <<" You have 280 UCAS points." << endl;
}
else if( points >= 1380)
{
cout <<" You have 240 UCAS points." << endl;
}
else if( points >= 1340)
{
cout <<" You have 200 UCAS Points." << endl;
}
else if ( points >= 1300)
{
cout <<" You have 160 UCAS Points." << endl;
}
}
我希望能够提示用户，如果他们输入除P，p，M，m，D或d之外的任何内容，那么程序会发出警告。
我在stackoverflow上注意到了这一点并找到了一个紧密的解决方案：
char c;
while (std::getline(std::cin, line))
{
// Iterate through the string one letter at a time.
for (int i = 0; i < line.length(); i++) {
c = line.at(i); // Get a char from string
// if it's NOT within these bounds, then it's not a character
if (! ( ( c >= 'a' && c <= 'z' ) || ( c >= 'A' && c <= 'Z' ) ) ) {
std::cout << "Error!" << std::endl;
// you can probably just return here as soon as you
// find a non-letter char, but it's up to you to
// decide how you want to handle it exactly
return 1;
}
}
}
答案 0 :(得分：1)
添加此功能：
bool isValidInput (char input) {
switch (input) {
case 'm':
case 'M':
case 'p':
case 'P':
case 'd':
case 'D':
return true;
default:
return false;
}
}
然后，要求输入：
for (index = 0; index < 18; index = index + 1)
{
cout << "What grade was achieved for " << lesson[index] << "?" << endl;
cin >> grades[index];
while (! isValidInput(grades[index])
{
cout << "Only m, p and d are valid inputs!";
cin >> grades[index];
}
}