56. Merge Intervals

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        if len(intervals) <= 1:
            return intervals
        else:
            res = []
            sorted_intervals = sorted(intervals)
            last_low = sorted_intervals[0][0]
            last_high = sorted_intervals[0][1]
                
            for i in range(1, len(sorted_intervals)):
                current = sorted_intervals[i]
                if current[0] <= last_high:
                    # merge, taking larger window
                    last_high = max(last_high, current[1])
                else:
                    # add last to res and track next interval
                    res.append([last_low, last_high])
                    last_low = current[0]
                    last_high = current[1]
                
                # encapsulate last interval
                if i == (len(sorted_intervals) - 1):
                    res.append([last_low, last_high])
                    
            return res