Daily question (02): inverted string

Learning enlightenment ：

1. First of all, this is an operation problem . The initial and final states are known . So consider “ Template mapping ”.

2. Basic skill ： Skilled double-layer cycle operation + Write the beginning and end conditions

3. Practice makes perfect ：auto Keyword application , Constantly assign values automatically +（C++STL The application of the library ）

4. Template mapping ---》 Data can be divided into letters , Numbers , Space ..... etc. . Data range can be changed （ For limiting letters ACII To judge ） Different settings of inverted format .

5.” Thinking problems “---》 A little recursive . If you don't analyze the fact that falling twice is equal to yourself （a And b XOR twice equals b,,, Sometimes ideas are abstract , It also depends on the inspiration at that time ）, You won't think of encapsulating words into one and then inverting , It may be reversed by traversing letters one by one , It's going to be a mess . The more boundary judgments , The more you use it, the easier it is to make mistakes . Cycle time , It means that it may bring O(n） Complexity , So be flexible and consider simplification .

6.STL Libraries are essentially data structures , Handle string and linked list problems , Draw on ideas and analytical methods , The basic skills of cooperating with circulation and writing judgment conditions . On the other side, we need help STL Traversal of Library , Simplified steps .

Even if there are many boundaries , Step by step , It's not easy to make a mistake

 Pseudo code 
1. I / O format , Header file , Complete variable initialization 
2. Global inversion 
3. Word inversion 
 Retrieve each word , Reverse a word once ,
 Inverse condition of each word ：  Right border （s.end） Space encountered 
4. Dealing with boundaries , String to /0 ending . Marks the end of retrieval and inversion 

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
	string s;
	getline(cin, s);
	// Flip the whole sentence 
	reverse(s.begin(), s.end());
	// Flip Words 
	auto start = s.begin();
	while (start != s.end())
	{
		auto end = start;
		while (start != s.end() && *end != ' ')
			end++;
		reverse(start, end);
		if (end != s.end())
			start = end + 1;
		else
			start = end;
	}
	cout<< s << endl;
	return 0;
}

Limited by knowledge , Just make a summary of the current basic learning , Ideas and knowledge are still insufficient , Please correct me if there is any mistake ！