如何理解这个C ++回文代码?
我最近找到了回文问题的解决方案,但是我不明白这部分代码是如何工作的(使用rbegin和rend).有人可以向我解释吗?
I recently came to the solution of the palindrome problem, but I do not understand how this part of code works (with rbegin and rend). Can someone explain it to me?
#include <iostream>
#include <string>
using namespace std;
bool checkPalindrome(string);
int main()
{
string inputString = "palindrom";
cout << checkPalindrome(inputString);
return 0;
}
bool checkPalindrome(std::string inputString)
{
return (inputString == string(inputString.rbegin(), inputString.rend()));
}
看看字符串构造函数:
...
(7) template <class InputIterator>
string (InputIterator first, InputIterator last);
您可以看到可以通过迭代器创建字符串. rbegin/rend迭代器是InputIterators,它指向它们所引用的相反位置:
You can see it is possible to create a string via iterators. The rbegin/rend iterators are InputIterators that points to the reverse positions that they refer:
rend() -->"My string"<-- rbegin()
也就是说,当您将rbegin()和rend()传递给字符串构造函数时,它将从字符串的结尾开始迭代到字符串的开头,从而创建反向的字符串:
That said, when you pass the rbegin() and rend() to the string constructor, it will iterate from the ending, to the beginning of the string, creating the inverted one:
iteration 0: "g" (currentIterator = rbegin() : push("g")
iteration 1: "n" (currentIterator = rbegin()+1 : push("n")
iteartion 2: "i" (currentIterator = rbegin()+2 : push("i")
...
iteration 8: "M" (currentIterator = rbegin()+8 : push("M")
iteration 9: rend() (currentIterator = rend() : stop iteration)
最后,operator ==()将检查字符串的等效性.
Finally, the operator==() will check for equivalence of the strings.