***The Skyline Problem (Leetcode 218)

Problem Link: https://leetcode.com/problems/the-skyline-problem/

import heapq
class Solution:
    def getSkyline(self, buildings: List[List[int]]) -> List[List[int]]:
        
        arr=[]
        for i in buildings:
            arr.append([i[0],-i[2]])
            arr.append([i[1],i[2]])
        arr.sort(key=lambda x:(x[0],x[1]))
        
        prevHeight=0
        ans=[]
        pq=[]
        for i in range(len(arr)):
            x=arr[i][0]
            # If starting point, 
            # add to the maxheap
            if(arr[i][1]<0):
                # Since, it is a maxheap,
                # insert -ve values
                heapq.heappush(pq,arr[i][1])
            else:
                # If it is the end of building
                for j in range(len(pq)):
                    if(-1*pq[j]==arr[i][1]):
                        break
                del pq[j]
                heapq.heapify(pq)
                
            # Add to the ans[] when height changes
            if(len(pq)>0):
                if(prevHeight!=-1*pq[0]):
                    ans.append([x,-1*pq[0]])
                    prevHeight=-1*pq[0]
            else:
                if(prevHeight!=0):
                    ans.append([x,0])
                    prevHeight=0
        
        return ans