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):

class Solution {
public:
    string reverseWords(string s) {
        int left = 0 ;
        for (int i = 0; i <= s.length(); i++) {
            if ( i == s.length() || s[i] == ' ') {   
                reverse(s.begin() + left , s.begin() + i) ;
                left = i+1 ;
            }
        }

        return s;
    }
};

C++(43ms):

class Solution {
public:
    string reverseWords(string s) {
        int left = 0 ;
        int num = 0 ;
        string ans = "" ;
        for(int i = 0 ; i < s.size() ; i++){
            if (s[i] != ' '){
                num++ ;
            }
            else if (s[i] == ' '){
                string t = s.substr(left,num) ;
                reverse(t.begin(),t.end());
                ans +=  t + ' ' ;
                left = i+1 ;
                num = 0 ;
            }

        }
        string t = s.substr(left,s.size()) ;
        reverse(t.begin(),t.end());
        ans += t ;
        return ans ;
    }
};

C++(29ms):

class Solution {
public:
    string reverseWords(string s) {
        for (int i = 0; i < s.length(); i++) {
            if (s[i] != ' ') {   
                int j = i;
                while(j < s.length() && s[j] != ' ')
                   j++;
                reverse(s.begin() + i, s.begin() + j);
                i = j;
            }
        }

        return s;
    }
};