菜单驱动逻辑错误导致无限循环

Question

全部。

这是我的第一篇文章。感谢您在这方面获得的所有帮助。

我已经测试了这些功能。他们工作正常。该计划的目的如下：

1) 用户输入一个字符串

2) 显示菜单

3) 用户选择

a) 数元音 b) 计算辅音 c) 计算字符串字母 d) 输入另一个字符串 e) 退出

4) 菜单不断循环，直到用户选择 E

我知道当我现在使用指针时遇到循环问题很尴尬，但事实就是这样。

感谢您对我简单的头脑的耐心等待！

代码如下：

#include<iostream>
#include<cctype>//Case conversion
using namespace std;

//FUNCTION PROTOTYPES
int countVowels(char *);
int countCons(char *);
int countAlpha(char *);

//FUNCTION MAIN

int main()
{
const int SIZE = 50;
char inputString[SIZE];

char a,b,c,d,e,f;
int choice,
    totalVowels,
    totalConsonants,
    totalLetters;

//Get the string from the user
cout << "Please enter a string consisting of 49 characters or less. ";
cin.getline(inputString, SIZE);


do{

    cout << "\nPlease make a selection from the menu:\n"
         << "a) Counts the vowels\n"
         << "b) Counts the connsonants\n"
         << "c) Counts the string\n"
         << "d) Enter another string\n"
         << "e) Quit" << endl;

    cout << "\nChoice is: ";
    cin >> choice;

    while (choice < 'a' || choice > 'e')
        {
            cout << "Invalid choice. Try again ";
            cin >> choice;
        }           
    //Call a function to count the vowels

    if (choice == tolower('a'))
    {
        totalVowels = countVowels(inputString);
        cout << "\n" << totalVowels << " Vowels" << endl;

    }


    //Call a function to count the vowels

    else if (choice == tolower('b'))
    {
        totalConsonants = countCons(inputString);
        cout << "\n" << totalConsonants << " Consonants" << endl;
    }

    //Call a function to count all letters

    else if (choice == tolower('c'))
    {
        totalLetters = countAlpha(inputString);
        cout << "\n" << totalLetters << " Letters" << endl;

    }

    //Write a new string

    else if (choice == tolower('d'))
    {
        cout << "Please enter a string consisting of 49 characters or less. 
";
        cin.getline(inputString, SIZE);

    }

} while (choice != tolower('e'));


return 0;
}

//FUNCTION DEFINITIONS

////Count the Vowels


 int countVowels(char* strPtr)
  {
    int vowelCount = 0; //Each time a vowel is counted

    while (*strPtr != '\0')
    {
        if (tolower(*strPtr) == 'a'
            ||tolower(*strPtr) == 'e' 
            ||tolower(*strPtr)== 'i' 
            ||tolower(*strPtr) == 'o' 
            ||tolower(*strPtr)== 'u')

            {
                vowelCount++;
            }
        strPtr++;
    }

    return vowelCount;
}

//Count the Consonants


int countCons(char* strPtr)
{

  int conCount = 0; //Each time a consonant  is counted

    while (*strPtr != '\0')
    {
        if (tolower(*strPtr) != 'a' 
            && tolower(*strPtr) != 'e' 
            && tolower(*strPtr) != 'i' 
            && tolower(*strPtr) != 'o'          //Clean this up
            && tolower(*strPtr) != 'u'          // See section 10.1 for more 
            && tolower(*strPtr) != ' '
            && tolower(*strPtr) != ','
            && tolower(*strPtr) != '?'
            && tolower(*strPtr) != '.'
            && tolower(*strPtr) != '!')

            {
                conCount++;
            }
        strPtr++;
    }

    return conCount;
}

//Count the Letters in the string


int countAlpha(char* strPtr)
{

  int alphaCount = 0;

    while (*strPtr != '\0')
    {
        if (isalpha (tolower(*strPtr))) 
        {
            alphaCount++;
        }
        strPtr++;
}

return alphaCount;  
}

Answer 1

问题是变量choice 被声明为具有int 类型。因此，当您输入一个字符时，就会发生输入流错误。在这种情况下，任何其他输入都将被忽略。

像这样声明变量

char choice;

考虑到这些变量

char a,b,c,d,e,f;

未在程序中使用。

还有这样的条件

choice == tolower('a')

意义不大。

随便写

choice == 'a'