问题：

输入一个文本，找出所有不同的单词（连续的字母序列），按字典序从小到大输出。单词不区分大小写。

样例输入

Adventures in Disneyland

Two blondes were going to Disneyland when they came to a fork in the
road. The sign read: “Disneyland Left.”

So they went home.

样例输出

a
adventures
blondes
came
disneyland
fork
going
home
in
left
read
road
sign
so
the
they
to
two
went
were
when

分析与解答

1.set用法
集合元素不重复，已从小到大排好序
具体参见https://blog.csdn.net/qq_40828914/article/details/80657356
2.字符串处理新方法
isalpha判断是否为字母
tolower(),大写变小写
stringstream ss(s);
ss>>buf 输入字符串，忽略空格

#include<iostream>
#include<string>
#include<set>
#include<sstream>using namespace std;int main(){string s,buf;while(cin>>s){for(int i=0;i<s.length();i++){if(isalpha(s[i])){s[i]=tolower(s[i]);}else{s[i]=' ';}}stringstream ss(s);while(ss>>buf){dict.insert(buf);}for(set<string>::iterator it=dict.begin();it!=dict.end();++it){cout<<*it<<"\n";}}   return 0;
}