如何将特定数量的字符转换为大写或小写并计算一个单词有多少个大写和小写字母

Question

旨在将单词转换为大写或小写的函数会将整个单词转换为大写或小写。 我想做的是将字符串中特定数量的字符转换为大写或小写。 以单词字符串为例。 如果用户只想将单词字符串中的字母S转换为大写，则输出应为：字符串。 此外，如果他们要转换的单词已经是大写或小写，则考虑到此功能。

示例：用户输入单词STRING。 想要将单词转换为STRing。 输出：STRING

#include <iostream> 
#include <string>  
#include <cctype> 
using namespace std;

//Function Prototype
int CountVowels(string, int &);
void ShowMenu(string &, char &);
void convertword(string &);

int main()
{
//Variables
string word;
char choice = '0';
int vowels = 0;

do
{
//Call Functions
ShowMenu(word, choice);

switch(choice)
{
case '1':
    cout << CountVowels(word, vowels);
    cout << endl << endl;
    break;

case '2':
    convertword(word);
    cout << endl << endl;
    break;
}

}while(choice != '5');

return 0;
}

void ShowMenu(string& word, char& choice)
{
cout <<"\t\tMENU\t\t" << endl
     <<"===========================================" << endl;
cout <<"1. Find the number of Vowels in a word" << endl
     <<"2. Convert to uppercase or lowercase " << endl
     <<"3. Count the number of uppercase letters  " << endl
     <<"4. Count the number of lowercase letters" << endl
     <<"5. Quit"
     <<"\n===========================================" << endl;
//Get menu choice and get word from user.
cout << endl;
cout <<"Enter a choice: ";
cin >> choice;

while((!isdigit(choice)) || (choice > '5'))
{
    cerr << "\nOut of range or invalid input. ";
    cin >> choice;
}

cin.ignore();

cout << endl;

cout << "Enter a word: ";
getline(cin, word, '\n');


}

int CountVowels(string word, int& vowelCount)
{
vowelCount = 0;

int numLetters = word.length();  //get the number of letters in a word

for (int i = 0; i < numLetters; i++)
{
    char letter = word[i];  //get the ith letter in the word

    if (letter == 'a' || letter == 'e' ||
        letter == 'i' || letter == 'o' ||
        letter == 'u' || letter == 'y' )
    {
        vowelCount++;
    }


}

cout << "\nThe number of vowels in this word is : ";

return vowelCount;
}

void convertword(string &word)
{
bool same = false;
char response;

cout << "\nWould you like to convert this word to uppercase or lowercase. " << endl;
cout << "\nType U for uppercase and l for lowercase. ";
cin >> response;

while(response != 'U' && response != 'l')
{
    cerr  << "\nInvalid input. ";
    cin >> response;
}

for(unsigned int i=0; i<word.length(); i++)
{
    if((response == 'U' && word[i]==toupper(word[i])))
    {
        same = true;
    }
    else if(response == 'U')
    {
        word[i]=toupper(word[i]);
    }
    else if((response == 'l' && word[i]==tolower(word[i])))
    {
        same = true;
    }
    else if(response == 'l')
    {
        word[i]=tolower(word[i]);
    }
}

cout << endl;

if(same)
{
    cout << "\nBased on your response, this word has already been converted. ";
}
else
    cout << "\nyour newly converted or unconverted word is : " << word;
    cout << endl;
}

Answer 1

// Capitalizes the first letter and all others are lower case.
size_t n = the number of characters you want.
if( !word.empty() )
{
    if( n > word.size() )
        n = word.size();
    for( size_t i = 0; i < word.size(); ++i )
        word[i] = toupper( word[i] );
    for( size_t i = n; i < word.size(); ++i )
        word[i] = tolower( word[i] );
}