Given an input string, reverse the string word by word.

For example,

Given s = "the sky is blue",

return "blue is sky the".

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分析

#include <iostream>

#include <string>

#include <cwctype>

#include <vector>

using namespace std;

// 去除字符串首尾的空格

string& trim(string &s)

{

	if(s.empty())

		return s;

	string::iterator iter;

	for(iter = s.begin(); iter != s.end()&& iswspace(*iter++););

	s.erase(s.begin(),--iter);

	for(iter = s.end(); iter != s.begin()&& iswspace(*--iter););

	s.erase(++iter,s.end());

	return s;

}

// 翻转字符串中的某一段子串

void reverseString(string &s, int begin, int end)

{

	for(; begin < end; begin++,end--)

	{

		char temp = s[begin];

		s[begin] = s[end];

		s[end] = temp;

	}

}

// 删除单词之间多余的空格

void delete_mult_spaces(string &s)

{

	string::iterator blank;

	string::iterator iter = s.begin();

	while(iter != s.end())

	{

		if(iswspace(*iter))

		{

			blank = iter + 1;

			while(iswspace(*blank))

				s.erase(blank);

			iter = blank;

		}

		iter++;

	}

}

void reverseWords(string &s)

{

	if (s.empty())

		return;

	s = trim(s);

	delete_mult_spaces(s);

	reverseString(s, 0, s.length()-1);

	int wbegin,wend;

	wbegin = wend = 0;

	for(size_t i = 0; i < s.length(); i++)

	{

		if(s[i] == ' ')

		{

			reverseString(s,wbegin,wend-1);

			wbegin = wend + 1;

		}

		wend++;

		// deal with the last word

		if(i == s.length()-1)

			reverseString(s,wbegin,wend-1);

	}

}

int main()

{

	vector<string> strs;

	strs.push_back("the sky is blue");

	strs.push_back("   the sky is blue");

	strs.push_back("the sky is blue   ");

	strs.push_back("the   sky is blue");

	strs.push_back("  the sky   is   blue   ");

	strs.push_back("");

	vector<string>::iterator iter;

	for(iter = strs.begin(); iter != strs.end(); iter++)

	{

		reverseWords(*iter);

		cout  << *iter << endl;

	}

	return 0;

}

1. 如何利用c++去除字符串首尾空格
2. 如何按照单词翻转字符串