Leetcode Study Day 11

Reverse Words in a String

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.

My solution

My solution is very intuitive, firstly, I iterate the whole string, and store all the word into an array. Then we iterate the array from back to front, and combine the words with a space.

class Solution {
public:
    string reverseWords(string s) {
        string output = "";
        string word ="";
        
        vector <string> words;
        int n = s.size();
        for (int i = 0; i < n; i++){
            if (s[i] == ' ' && word.size() != 0){
                words.push_back(word);
                word = "";
                continue;
            }
            if (s[i] == ' ' && word.size() == 0)
                continue;
            word += s[i];
        }
        if (word != "")
            words.push_back(word);
        int words_size = words.size();
        for (int i = words_size-1; i >= 0; i--){

            output += words[i];
            if (i != 0) output += ' ';
        }
        return output;
    }
};