题解 | #计算某字符出现次数#

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

int main()
{
    string str = "";
    char s;
    int ans=0;
    getline(cin, str);//读取一行，不能扔用cin，因为有空格
    scanf("%c", &s);
    //tolower(char):把字母字符转换成小写，非字母字符不做出处理。
    //touppre(char)函数是把字符串都转化为大写字母

    for (int i = 0; i < str.length(); ++i)
    {
        if ((str[i] >= 'a'&&str[i] <= 'z') || (str[i] >= 'A'&&str[i] <= 'Z') || (str[i] >= '0'&&str[i] <= '9')||(str[i]==' '))
        {
            if (tolower(str[i]) == tolower(s))
                ans++;
        }
        else//输入有误
        {
            printf("Input error");
            break;
        }
    }
    printf("%d", ans);
    return 0;
}