That is an on-campus interview at New York. It consists of two rounds back-to-back. In each round, you face an interviewer in a small room. You may choose to write your code on a whiteboard or on white paper. My interviewer provided me with his laptop, so I could code in a Google Doc on his machine.

Round 1

Given a bitmap, use a Quadtree data structure to represent the bitmap. The maps are all squares with black or white pixels, and the length of the map is 2^n. You can always divide the map into 4 smaller parts. Then, given a root node of a Quadtree, calculate the total number of black pixels in this map.

Follow-up: Given two root nodes, generate the intersection of these two maps.

Round 2

LeetCode Triangle

Given a triangle of integers, find the maximum path sum from the top point to the bottom.

Follow-up: Print out the path of the maximum sum.