179. Largest Number

给定一组非负整数 nums，重新排列每个数的顺序（每个数不可拆分）使之组成一个最大的整数。

• Runtime: 116 ms, faster than 21.10%
• Memory Usage: 40.5 MB, less than 44.66%

/**
 * @param {number[]} nums
 * @return {string}
 */
var largestNumber = function(nums) {
  nums.sort((x, y) => {
    let sx = 10;
    let sy = 10;
    while (sx <= x) {
      sx *= 10;
    }
    while (sy <= y) {
      sy *= 10;
    }
    return (sx * y + x) - (sy * x + y);
  })
  if (nums[0] === 0) {
    return '0';
  }
  return nums.join('');
};