138. Copy List with Random Pointer

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        
        intervals.sort(key=lambda x: x[0])
        
        merged = []
        
        for i in intervals:
            if not merged or merged[-1][1] < i[0]:
                merged.append(i)
            else:
                merged[-1][1] = max(merged[-1][1], i[1])
        
        return merged
        

Runtime: 80 ms, faster than 89.80% of Python3 online submissions for Merge Intervals.
Memory Usage: 16.2 MB, less than 9.17% of Python3 online submissions for Merge Intervals.

python 미쳤나...??
이거 속도가 5%에서 89.80% 까지 너무 다양한디용;;