将string按空格为界单词位置反转，并转换大小写

例如：This is a sample ->SAMPLE A IS tHIS

#include<iostream>
#include<string>
#include <stack>
using namespace std;
class Transform
{
public:
    string trans(string& s, int n)
    {
        //首先转换大小写
        for(int i = 0;i < n;++i)
            {
                if(s[i] >= 'a' && s[i] < 'z')
                {
                    s[i] -= 32;
                }
                else if(s[i] > 'A' && s[i] < 'Z')
                {
                    s[i] += 32;
                }
        }
        //将字符串整个逆转
        int start = 0,end = n - 1;
        while(start < end)
        {
            swap(s[start],s[end]);
            start++;
            end--;
        }
        //把单词逆转回来
        string ret;
        stack<char> sk;
        int index = 0;
        while(index < n)
        {
            while(index < n&&s[index] != ' ')//注意这里判断时为了防止下标越界，要加上判断下标的条件
            {
                sk.push(s[index]);
                ++index;
            }
            ++index;
            while(!sk.empty())
            {
                ret += sk.top();
                sk.pop();
            }
            ret += ' ';
        }
        cout<<ret;
        return ret;
    }
};
int main()
{
    Transform t;
    string s("This is a sample");
    t.trans(s,16);

    return 0;
}