题解 | #计算某字母出现次数#

#include <iostream>
#include <string>
#include <stdlib.h>
using namespace std;
#define CHAR_COUNT 1

/*
思路：输入的字符串、字符分为大小写，大写字符与小写字符相差32位，如果输入字符oneChar为大写，则将字符串字符strIn[i]大写与oneChar
比较或小写字符 与 字符oneChar+32进行比较；如果输入字符oneChar为小写，则将字符串字符strIn[i]小写与oneChar或
字符串字符strIn[i]大写与字符oneChar-32进行比较；
*/
#ifdef CHAR_COUNT
int OneCharCount(string strIn, char oneChar)
{
    if(strIn.length() == 0) {
        return 0;
    }
   
    int charCount = 0;
    int strInLen = strIn.length();
    if(oneChar >= 'A' && oneChar <= 'Z') {
        for(int i = 0; i < strInLen; i++) {
            if(strIn[i] == oneChar || strIn[i] -32 == oneChar) {
                charCount++;
            }
        }
    } else if(oneChar >= 'a' && oneChar <= 'z') {
        for(int i = 0; i < strInLen; i++) {
            if(strIn[i] + 32 == oneChar || strIn[i] == oneChar) {
                charCount++;
            }
        }
    } else {
         for(int i = 0; i < strInLen; i++) {
             if(strIn[i] == oneChar) {
                 charCount++;
             }
         }
    }

    return charCount;
}
#else

/*
思路：字符串的字符strIn[i]与输入字符oneChar比价，输入字符oneChar的大小写与strIn[i]比较
*/
int  OneCharCount2(string strIn, char oneChar)
{
    if(strIn.length() == 0) {
        return 0;
    }
    
    int charCount = 0;
    int strInLen = strIn.length();
    if(oneChar >= 'A' && oneChar <= 'Z') {
        for(int i = 0; i < strInLen; i++) {
            if(toupper(strIn[i]) == oneChar || strIn[i] == oneChar) {
                charCount++;
            }
        }
    } else if(oneChar >= 'a' && oneChar <= 'z') {
        for(int i = 0; i < strInLen; i++) {
            if(tolower(strIn[i]) == oneChar || strIn[i] == oneChar) {
                charCount++;
            }
        }
    } else {
        for(int i = 0; i < strInLen; i++) {
             if(strIn[i] == oneChar) {
                 charCount++;
             }
         }
    }
    return charCount;
}
#endif

int main()
{
    string strIn;
    char oneChar;

     getline(cin, strIn);
     //oneChar = getchar();
    cin>>oneChar;
#ifdef CHAR_COUNT
    cout<<OneCharCount(strIn, oneChar)<<endl;
#else
     cout<<OneCharCount2(strIn, oneChar)<<endl;
#endif
    return 0;
}