[LeetCode][JavaScript]Reverse Words in a String

Reverse Words in a String

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.

click to show clarification.

Clarification:

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

https://leetcode.com/problems/reverse-words-in-a-string/

---

反转字符串中的单词。

万能的正则表达式。

/**
 * @param {string} str
 * @returns {string}
 */
var reverseWords = function(str) {
    return str.trim().split(/s+/).reverse().join(' ');
};

正常解法， javascript 不能in-place改变字符串，开了个变量。

/**
 * @param {string} str
 * @returns {string}
 */
var reverseWords = function(str) {
    var start = -1, end, i, result = "";
    for(i = 0; i < str.length; i++){
        if(!/s/.test(str[i])){
            if(start === -1){
                start = i;
            }    
            if(start !== -1 && (!str[i + 1] || /s/.test(str[i + 1]))){
                end = i;
                result = str.substring(start ,end + 1) + ' ' + result;
                start = -1;
                i++;
            }
        }
    }
    return result.trim();
};