# 179. Largest Number

<https://leetcode.com/problems/largest-number/>

## solution

* 自定义排序key: 两两比较 `functools.cmp_to_key`

```python
import functools

class Solution:
    def largestNumber(self, nums: List[int]) -> str:
        def comparator(s1, s2):
            if int(s1 + s2) < int(s2 + s1):
                return -1
            if int(s1 + s2) > int(s2 + s1):
                return 1
            return 0

        nums = [str(i) for i in nums]
        nums = sorted(nums, key = functools.cmp_to_key(comparator), reverse=True)
        ans = '0' if nums[0] == '0' else ''.join(nums)
        return ans
```

时间复杂度：O(sort)\
空间复杂度：O(n)
