该错误始于 cin.getline ( string, 25, '\n' ); 或它下面的行(strtod)。如果我使用 cin,它可以工作,但我不能退出。如果我输入任何不是双精度的,就会运行一个无限循环。需要帮忙。基本上,第一次迭代运行,不要求输入,所以用户把数学问题弄错了。第二次迭代工作正常。接下来也很好。如果我退出,使用 q,我会被转回到模式选择器。选择一种模式后,第一次迭代会再次出现该错误。下一次迭代它就消失了。
int main()
{
char choice, name[25], string[25], op;
int operator_number, average, difference, first_operand, second_operand, input, answer, total_questions = 0, total_correct = 0;
double dfirst_operand, dsecond_operand, dinput, danswer, percentage;
bool rounding = false;
srand ( time(NULL) );
cout << "What's your name?\n";
cin.getline ( name, 25, '\n' );
cout << '\n' << "Hi, " << name << ".";
do {
do {
cout << "\nWhich math operations do you want to practice?\n 1. Addition\n 2. Subtraction\n 3. Multiplication\n 4. Division\n 5. Mixed\n 6. Difference of squares multiplication.\nChoose a number (q to quit).\n";
cin >> choice;
} while( choice < '1' || choice > '6' && choice!= 'q');
cout << "\n";
switch(choice) {
case '1':
while( string[0]!= 'q') {
dfirst_operand = rand() % 15 + 1;
dsecond_operand = rand() % 15 + 1;
danswer = dfirst_operand + dsecond_operand;
cout << dfirst_operand << " + " << dsecond_operand << " equals?\nEnter q to quit.\n";
cin.getline ( string, 25, '\n' );
dinput = strtod( string,NULL);
//cin >> dinput;
if(string[0]!='q') {
++total_questions;
if(dinput==danswer) {
++total_correct;
cout << "Correct. " << total_correct << " correct out of " << total_questions << ".";
} else {
cout << "Wrong. " << dfirst_operand << " + " << dsecond_operand << " equals " << danswer << ".\n" << total_correct << " correct out of " << total_questions << ".";
};
percentage = floor(10000 * (float) total_correct / total_questions)/100;
cout << ' ' << percentage << "%.\n\n";
}
}
break;
}
} while(choice!='q');
return 0;
}