ReverseWordsInString.cpp

class Solution {
public:
    string reverseWords(string s) {
        int n = s.size();
        string ans = "";
        string temp = "";

        for(int i=n-1;i>=0;i--){
            if(s[i] != ' '){
                temp += s[i];
            }
            else{
                if(!temp.empty()){
                    reverse(temp.begin(),temp.end());
                    if(!ans.empty()){
                        ans += ' ';
                    }
                }
                ans += temp;
                temp.clear();
            }
        }

        if(!temp.empty()){
            reverse(temp.begin(),temp.end());
            if(!ans.empty()){
                ans += " ";
            }
            ans += temp;
        }
        return ans;
    }
};

/*
Given an input string s, reverse the order of the words.

A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.

Return a string of the words in reverse order concatenated by a single space.

Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces.

 

Example 1:

Input: s = "the sky is blue"
Output: "blue is sky the"
Example 2:

Input: s = "  hello world  "
Output: "world hello"
Explanation: Your reversed string should not contain leading or trailing spaces.
Example 3:

Input: s = "a good   example"
Output: "example good a"
Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.
 

Constraints:

1 <= s.length <= 104
s contains English letters (upper-case and lower-case), digits, and spaces ' '.
There is at least one word in s.
 

Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?
*/