179. Largest-Number

/**
 * @param {number[]} nums
 * @return {string}
 */
var largestNumber = function(nums) {
    nums.sort((a,b) => (b + "" + a) - (a + "" + b));
    let res = nums.join("");
    
    return res[0] === '0' ? '0' : res;
};

class Solution:
    def largestNumber(self, nums: List[int]) -> str:
        nums_as_str = [str(num) for num in nums]
        nums_as_str.sort(key=cmp_to_key(self._compare_numbers))

        if nums_as_str[0] == '0':
            return '0'
        return "".join(nums_as_str)

    def _compare_numbers(self,a: str, b: str) -> int:
        if a + b < b + a:
            return 1
        return -1