按照单词反转字符串，再整体反转
- 时间复杂度O(n)，空间复杂度O(1)
- Runtime: 88 ms, faster than 99.40%
- Memory Usage: 46.2 MB, less than 31.74%
/**
* @param {character[]} s
* @return {void} Do not return anything, modify s in-place instead.
*/
var reverseWords = function(s) {
s = s.reverse();
let left = 0;
for (let i = 0; i < s.length; i++) {
if(s[i + 1] === ' ' || s[i + 1] === undefined) {
let right = i;
while(left < right) {
let tmp = s[left];
s[left++] = s[right];
s[right--] = tmp
}
left = i + 2;
}
}
return s;
};
