from functools import cmp_to_key

class Solution:
    def largestNumber(self, nums: List[int]) -> str:
        def cmp_func(x, y):
            """Sorted by value of concatenated string increasingly."""
            print(x,y)
            if x + y > y + x:
                return 1
            elif x == y:
                return 0
            else:
                return -1
            
        # Build nums contains all numbers in the String format.
        nums = [str(num) for num in nums]
        print(nums)
        # Sort nums by cmp_func decreasingly.
        nums.sort(key = cmp_to_key(cmp_func), reverse = True)
        
        # Remove leading 0s, if empty return '0'.
        return ''.join(nums).lstrip('0') or '0
```'

Input: nums = [3,30,34,5,9]

stdout
['3', '30', '34', '5', '9']
5 9
34 5
30 34
3 30
3 5
3 34
3 30


Output
"9534330"
Expected
"9534330"