LeetCode - Reverse Words in a String

最新推荐文章于 2021-11-14 17:00:20 发布

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本文介绍了一种高效的字符串反转算法，该算法能够逐词反转输入的字符串，并处理多个空格及前后空白字符的问题。通过实例演示了如何使用C++实现这一算法。

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

For example,
Given s = "the sky is blue",
return "blue is sky the".

click to show clarification.

Clarification:

What constitutes a word?
A sequence of non-space characters constitutes a word.
Could the input string contain leading or trailing spaces?
Yes. However, your reversed string should not contain leading or trailing spaces.

How about multiple spaces between two words?
Reduce them to a single space in the reversed string.

class Solution {
public:
    void reverse(string &s, int begin, int end){
	   int p=begin;
	   int q=end-1;
	   while(p < q){
	       char tmp = s[p];
		   s[p++]=s[q];
		   s[q--]=tmp;
	   }
	}

    void reverseWords(string &s) {
      if( s.size()==0){
	      return;
	  }
	  
	  int index=0,tmp=index;
	  
	  while(tmp<s.size()){
          while(tmp<s.size() && s[tmp]==' '){
              tmp++;
          }
          while(tmp<s.size() && s[tmp]!=' '){
              s[index++]=s[tmp++];
          }
          
          if(tmp<s.size()){
             s[index++]=' ';
             tmp++;
          }  
      }
      
      if(index ==0 ){
         s="";
         return;
      }
       
      if(s[index-1]==' '){
          index--;
      }
      
      s.erase(index,s.size()-index);
       
      reverse(s,0,index);

      int begin=0,end=0;
      while(end<s.size()){
         begin=end;
	    
		 while(end<s.size() && s[end]!=' '){
            end++;
		 }
       
	     reverse(s,begin,end);
         
         end++;
	  }
    }
};