LeetCode: 557Reverse Words in a String III(easy)

题目：

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

Input: "Let's take LeetCode contest"
Output: "s'teL ekat edoCteeL tsetnoc"

Note: In the string, each word is separated by single space and there will not be any extra space in the string.

代码：

 class Solution {
 public:
     string reverseWords(string s) {
         stack<char> tem;
         string result;
         string s1 = s + ' ';
         for (auto c : s1){
             if ( c != ' ')
                 tem.push(c);
             else {
                 while(!tem.empty()){
                     result = result + tem.top();
                     tem.pop();
                 }
                 result = result + ' ';
             }
         }
         result = result.substr(, result.length()-);
         return result;
     }
 };

运行时间：772ms

别人的：

 class Solution {
 public:

     string reverseWords(string s) {
         string result(s.length(), );
         int start = ;
         int end = s.find();
         while (end != -) {
             for (int i = start; i < end; ++i)
                 result[end - (i - start) - ] = s[i];
             start = end + ;
             end = s.find(, start);
         }
         end = s.length();
         for (int i = start; i < end; ++i)
             result[end - (i - start) - ] = s[i];
         return result;
     }
 };

运行时间：26mm

栈比较耗时间？