344. 反转字符串（算法200题-20）

/**
 * @param {character[]} s
 * @return {void} Do not return anything, modify s in-place instead.
 */
var reverseString = function(s) {
  if(s.length < 2) return
  let start = 0, end = s.length - 1
  while(start <= end) {
    s[start] !== s[end] ? [s[start], s[end]] = [s[end], s[start]] : null
    start += 1
    end -= 1
  }
};