Leetcode 56 problem.

Python

• Time complexity: $O(n * log(n))$ - n is a length of an array
• Auxiliary space: $O(1)$ - constant amount of space

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        
        # Sort by an intervals' start point
        intervals.sort(key = lambda x: x[0])
        i = 1
        
        while i < len(intervals):
            
            previousStart = intervals[i-1][0]
            previousEnd = intervals[i-1][1]

            currentStart = intervals[i][0]
            currentEnd = intervals[i][1]
            
            # if current previousStart is between previous interval
            if previousStart <= currentStart <= previousEnd:
                
                # current interval is minimum and maximum values of starts and ends
                intervals[i] = [min(previousStart, currentStart), max(previousEnd, currentEnd)]
                
                # delete previous interval from intervals
                intervals = intervals[:i-1] + intervals[i:]
            
            else:
                i += 1
                
        return intervals