STL语法——集合：set 安迪的第一个字典（Andy's First Dictionary,UVa 10815）

Description

Andy, , has a dream - he wants to produce his very own dictionary. This is not an easy task for him, as the number of words that he knows is, well, not quite enough. Instead of thinking up all the words himself, he has a briliant idea. From his bookshelf he would pick one of his favourite story books, from which he would copy out all the distinct words. By arranging the words in alphabetical order, he is done! Of course, it is a really time-consuming job, and this is where a computer program is helpful.

You are asked to write a program that lists all the different words in the input text. In this problem, a word is defined as a consecutive sequence of alphabets, in upper and/or lower case. Words with only one letter are also to be considered. Furthermore, your program must be CaSe InSeNsItIvE. For example, words like "Apple", "apple" or "APPLE" must be considered the same.

Input

The input file  lines. An input line has at most  characters. Input is terminated by EOF.

Output

Your output should give a list of different words that appears .

Sample Input

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.

Sample Output

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

1.中文翻译

大体的中文意思就是：输入一个文本，找出所有不同的单词（连续的字母序列），按字典序列从小到大输出。单词不区分大小写，输入输出和上面一样。

2.分析

这个题比较简单，我学习的是《算法竞赛入门经典》这本书的代码。

1.学会运用set容器；（有个小知识点，set容器，元素只能出现一次，并且插入可以从小到大排序）

2.学习字符函数库中常用的函数

3.学会stringstream（可参考这篇博文：http://blog.csdn.net/xw20084898/article/details/21939811）

4.最后运行记得是在空行 ctrl+z +回车。（至于为什么，参考博文：http://blog.csdn.net/kevin_ut/article/details/8576740）

3.说明

set是一个集合和康托前辈的一样集合中的元素不重复且集合中的元素是有序的（自动有序化） TY菌介绍说其内部实质是一个平衡树

set不是数组只能通过迭代器（iterator）把里面的元素倒出来迭代器相当于是指针扫描的是地址因此输出的时候需要用*variation

4.声明

需要用到头文件set

set<string> dict; 建立一个集合其名为dict 基类型是string

5.常用函数

dict.begin() dict.end()返回集合最初和最后的元素的地址

这是写这个例题用到的

6.代码

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

 set<string> dict;//set up a set called dict-short for dictionary,and it's based on string type;  

 int main(){
     string s,buf;
     while (cin>>s){
         ;i<s.length();i++)
           if (isalpha(s[i])) s[i]=tolower(s[i]);//if it's an letter,turn it lowercase.Others turn space and use stringstream to leave it out=ignore it
           else s[i]=' ';
         stringstream ss(s);
         while (ss>>buf) dict.insert(buf);//insert it into the set which is already in order,TYkon said it's a balanced tree inside
     }
     for (set<string>::iterator it=dict.begin();it!=dict.end();++it)//iterator just like a point,scan it from beginning to end and output
       cout<<*it<<endl;//NOTICE output by point
     ;
 }

还是英文注释不过看懂应该问题不大

isalpha()判断是否是字母如果是就用头tolower()转换成小写否则就转为空格这样是为了字符串流重读入的时候能够把空格去掉

特别强调一下本例中出现的迭代器

 for (set<string>::iterator it=dict.begin();it!=dict.end();++it)//iterator just like a point,scan it from beginning to end and output
       cout<<*it<<endl;//NOTICE output by point

迭代器iterator相当于是个类型 it是一个变量基类型是iterator 它从开始扫到结尾的前一个【据TY菌解释像数组一样最后一位是没有值的数组是一个结束标志不知集合最后是什么】输出的时候由于it扫描的是地址要输出*it

这个好像用到了stl set的语法....

显然对于set我还知之甚少还需要在今后的学习中不断掌握

今天晚上此时已是0：15，写完博客，明天上课.....

本文部分引用http://blog.csdn.net/ametake