rope(转载)
谈c++ pb_ds库(一)rope大法好
(转载)原文链接 https://www.cnblogs.com/keshuqi/p/6257642.html
参考资料
1)官方说明
支持
sorry,cena不支持rope
声明
1)头文件
#include<ext/rope>
2)调用命名空间
using namespace __gnu_cxx;
底层原理
查了资料,大概可以称作可持久化平衡树,因为rope适用于大量、冗长的串操作,而不适合单个字符操作官方说明如下:
Though ropes can be treated as Containers of characters, and are almost Sequences, this is rarely the most efficient way to accomplish a task. Replacing an individual character in a rope is slow: each character replacement essentially consists of two substring operations followed by two concatenation operations. Ropes primarily target a more functional programming style.Inserting a character in the middle of a 10 megabyte rope should take on the order of 10s of microseconds, even if a copy of the original is kept, e.g. as part of an edit history.It is possible to view a function producing characters as a rope. Thus a piece of a rope may be a 100MByte file, which is read only when that section of the string is examined. Concatenating a string to the end of such a file does not involve reading the file. (Currently the implementation of this facility is incomplete.)
另,根据网上资料,rope本质是封装好的类似块状链表的东东,有人说是logn的,但也有说是n^0.5的。rope不支持一切数值操作,如第k大
小知识
先介绍几个可能使用到的函数
1)append()
string &append(const string &s,int pos,int n);//把字符串s中从pos开始的n个字符连接到当前字符串的结尾
或
a.append(b);
2)substr()
s.substr(0,5);//获得字符串s中从第零位开始长度为5的字符串(默认时长度为刚好开始位置到结尾)
定义/声明
rope<char> str;
also
<crope>r="abcdefg"
具体内容
总的来说,
1)运算符:rope支持operator += -= + - < ==
2)输入输出:可以用<<运算符由输入输出流读入或输出。
3)长度/大小:调用length(),size()都可以哦
4)插入/添加等:
push_back(x);//在末尾添加x
insert(pos,x);//在pos插入x,自然支持整个char数组的一次插入
erase(pos,x);//从pos开始删除x个
copy(pos,len,x);//从pos开始到pos+len为止用x代替
replace(pos,x);//从pos开始换成x
substr(pos,x);//提取pos开始x个
at(x)/[x];//访问第x个元素
访问
1)迭代器:不说,在竞赛是超时大忌
2)单点访问,直接用数组形式调用下标即可