179. Largest Number

主要考的自定义函数？

class Solution(object):
    def largestNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: str
        """
        def comp(a, b):
            if a + b > b + a:
                return 1
            elif a + b < b + a:
                return -1 
            else:
                return 0
        nums = [str(num) for num in nums]
        nums.sort(comp, reverse=True)
        ans = ''.join(nums)
        return '0' if int(ans) == 0 else ans