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Leetcode Binary Tree Level Order Traversal II Java Solution

Given a binary tree, return the bottom-up level order traversal of its nodes’ values. (ie, from left to right, level by level from leaf to root). For example:Given binary tree [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 return its bottom-up level order traversal as: [ [15,7], [9,20], [3] ] Solution:We can solve it multiple ways…… Continue reading Leetcode Binary Tree Level Order Traversal II Java Solution

Leetcode Reconstruct Itinerary Java Solution

Given a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order. All of the tickets belong to a man who departs from JFK. Thus, the itinerary must begin with JFK. Note: If there are multiple valid itineraries, you should return the itinerary that has the smallest lexical order…… Continue reading Leetcode Reconstruct Itinerary Java Solution

Leetcode 200 Number of Islands (Java) With Video Explanation

Given a 2d grid map of ‘1’s (land) and ‘0’s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water. Example : Input: 11000 11000 00100 00011 Output: 3 Solution: We…… Continue reading Leetcode 200 Number of Islands (Java) With Video Explanation