557. Reverse Words in a String III

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"



C++(22ms):

 1 class Solution {
 2 public:
 3     string reverseWords(string s) {
 4         int left = 0 ;
 5         for (int i = 0; i <= s.length(); i++) {
 6             if ( i == s.length() || s[i] == ' ') {   
 7                 reverse(s.begin() + left , s.begin() + i) ;
 8                 left = i+1 ;
 9             }
10         }
11 
12         return s;
13     }
14 };



C++(43ms):

 1 class Solution {
 2 public:
 3     string reverseWords(string s) {
 4         int left = 0 ;
 5         int num = 0 ;
 6         string ans = "" ;
 7         for(int i = 0 ; i < s.size() ; i++){
 8             if (s[i] != ' '){
 9                 num++ ;
10             }
11             else if (s[i] == ' '){
12                 string t = s.substr(left,num) ;
13                 reverse(t.begin(),t.end());
14                 ans +=  t + ' ' ;
15                 left = i+1 ;
16                 num = 0 ;
17             }
18 
19         }
20         string t = s.substr(left,s.size()) ;
21         reverse(t.begin(),t.end());
22         ans += t ;
23         return ans ;
24     }
25 };

C++(29ms):

 1 class Solution {
 2 public:
 3     string reverseWords(string s) {
 4         for (int i = 0; i < s.length(); i++) {
 5             if (s[i] != ' ') {   
 6                 int j = i;
 7                 while(j < s.length() && s[j] != ' ')
 8                    j++;
 9                 reverse(s.begin() + i, s.begin() + j);
10                 i = j;
11             }
12         }
13 
14         return s;
15     }
16 };