程序代码：

#include<iostream>
#include<string>
#include<cctype>
using std::cin;
using std::cout;
using std::endl;
using std::string;
using string::size_type;
int main()
{
    string user;
    cout<<"Input a sentence, Spaces into ^"<<endl<<endl;
    cin>>user;
    user[0]=toupper(user[0]);
    for (size_type sign=1;sign!=user.size();++sign)
    {
        if((user[sign] == '.') || (user[sign] == '?') || (user[sign] == '!')|| (user[sign] == ';'))
        {
            user[sign + 1] = toupper(user[sign + 1]);
        }
        if(user[sign]=='^')
        {
            user[sign]=' ';
        }
    }
    cout<<endl<<user<<endl<<endl;
    return 0;
}

程序代码：

    string user;
    cin>>user;
    user[0]=toupper(user[0]);//把句子的第一个字母变成大写
    for (size_type sign=1;sign!=user.size();++sign)
    {
        if(ispunct(sign))//如果遇到标点符号
        {
            size_type signA;
            switch(sign)
            {
            case '.'://如果标点符号是"."或"!"或"?"，将标点符号后一位的字母变成大写
                signA=user[sign+1];
                user[signA]=toupper(user[signA]);
                break;
            case '?':
                signA=user[sign+1];
                user[signA]=toupper(user[signA]);
                break;
            case '!':
                signA=user[sign+1];
                user[signA]=toupper(user[signA]);
                break;
            default:
                break;
            }
        }
    }
    cout<<user<<endl;
    return 0;