在处理 C 字符串时，如何将用户的第一个输入替换为当前输入

我在尝试用其他用户输入替换用户输入时遇到问题。

爱狗"，然后我们问他们是否要输入其他字符串，他们输入"我吃了很多冰淇淋"。

如何将用户的第一个输入替换为当前输入？

// Function Prototype
int countVowels(char * str);
int countCons(char * str);
int main()
{
const int SIZE = 81;          // Max size of the array
                              //const int V_SIZE = 6;         // Size of the vowel array
char newSentence[SIZE];
char userString[SIZE];
//char vowels[V_SIZE] = {'a', 'e', 'i', 'o', 'u'};
char choice;                  // To hold the menu choice
char *strPtr = userString;    // Declare and initialize the pointer
char *sentPtr = newSentence;
                              // Get the string from the user
cout << "Please enter a string. (Maximum of 80 characters) :nn";
cin.getline(userString, SIZE);
do{
    // Display the menu and get a choice
    cout << "nnA. Count the number of vowels in the string n";
    cout << "B. Count the number of consonants in the string n";
    cout << "C. Enter another string n";
    cout << "D. Exit the program nn";
    cout << "Please make your selection: ";
    cin >> choice;
    // Menu selections
    if (tolower(choice) == 'a')
    {
        countVowels(userString);
        cout << "This string contains " << countVowels(userString);
        cout << " vowels. n";
    }
    else if (tolower(choice) == 'b')
    {
        countCons(userString);
        cout << "This string contains " << countCons(userString);
        cout << " consonants. n";
    }
    else if (tolower(choice) == 'c')
    {
        cout << "Please enter other string: ";
        cin.getline(newSentence, SIZE);
        userString.replace();
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), 'n');
    }
    else
    {
        system("PAUSE");
        return 0;
    }
} while (choice != 'D');
}

我在菜单选择 C 时遇到问题。如何将 userString 替换为 newSentence？