TeX is a typesetting language developed by Donald Knuth. It takes source text together with a few typesetting instructions and produces, one hopes, a beautiful document. Beautiful documents use `` and " to delimit quotations, rather than the mundane " which is what is provided by most keyboards. Keyboards typically do not have an oriented double-quote, but they do have a left-single-quote ` and a right-single-quote '. Check your keyboard now to locate the left-single-quote key `(sometimes called the ``backquote key") and the right-single-quote key ' (sometimes called the ``apostrophe" or just ``quote"). Be careful not to confuse the left-single-quote ` with the ``backslash" key \. TeX lets the user type two left-single-quotes `` to create a left-double-quote `` and two right-single-quotes '' to create a right-double-quote ''. Most typists, however, are accustomed to delimiting their quotations with the un-oriented double-quote ".
If the source contained
"To be or not to be," quoth the bard, "that is the question."
then the typeset document produced by TeX would not contain the desired form:
``To be or not to be," quoth the bard, ``that is the question."
In order to produce the desired form, the source file must contain the sequence:
``To be or not to be,'' quoth the bard, ``that is the question.''
You are to write a program which converts text containing double-quote (") characters into text that is identical except that double-quotes have been replaced by the two-character sequences required by TeX for delimiting quotations with oriented double-quotes. The double-quote (") characters should be replaced appropriately by either `` if the " opens a quotation and by '' if the " closes a quotation. Notice that the question of nested quotations does not arise: The first "must be replaced by ``, the next by '', the next by ``, the next by '', the next by ``, the next by '', and so on.
Input
Input will consist of several lines of text containing an even number of double-quote (") characters. Input is ended with an end-of-file character.
Output
The text must be output exactly as it was input except that:
- the first " in each pair is replaced by two ` characters: `` and
- the second " in each pair is replaced by two ' characters: ''.
Sample Input
"To be or not to be," quoth the Bard, "that is the question". The programming contestant replied: "I must disagree. To `C' or not to `C', that is The Question!"
Sample Output
``To be or not to be,'' quoth the Bard, ``that is the question''. The programming contestant replied: ``I must disagree. To `C' or not to `C', that is The Question!''
这个题的意思是把输入文件中的"替换成``，
"替换成''
按照紫书刘汝佳的算法，这个东西不需要保存直接读入读出即可。
代码：
#include <iostream> using namespace std; main() { int q=1; char c; while((c=getchar())!=EOF) { if(c=='"') { printf("%s",q?"``":"''"); q=!q; } else printf("%c",c); } }
经过实验发现c=getchar()可以避免空格的问题，在不存储输入一行的string中有着很好的作用且（c=getchar())!=EOF还是比较少用需要注意。
这里需要一个开关，刘汝佳给出的做法是q=!q;这样直接保证bool的true和false转换。
我的思路是直接用string类搜索求解（但是目前还不知道哪里出现了问题。。。）
在此整理一下STL的基本对象函数erase insert
xxxx.insert()
我个人简单的感觉分为两类，一类是set之类的容器直接用
insert(value)即可
另一种就是string之类的容器需要进行定位
string可以用数组一样的下标去表示。
insert(index,value,cnt)
也可以用迭代器进行
insert(pos,value,cnt)
cnt代表插入的个数而vector之类的容器应该是只能用迭代器去进行插入。
还有一个关键的地方是这些容器的cnt都是在value前面，例如vec.insert(pos,cnt,value)
xxxx.erase()
同样也是分两类。set的容器因为值都是特殊的，所以可以用特殊的erase(key_value)来进行删除的操作。
其他的还有string是特殊的，它可以用index来进行删除但是注意：
如果你只写一个index是从index到pos一块删除，所以要用index,index+1来进行删除，当然也可以用pos的迭代器。
其他的没有什么特别的了，基本上，一般就是pos，pos,pos+n.