211. Design Add and Search Words Data Structure
- By
Wayne
This problem asks us to build a word dictionary, which is obviously to use Trie. But it also asks to support dots ‘.’ where dots can match any letter.
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Java
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208. Implement Trie (Prefix Tree)
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This problem is asking us to implement a very basic Trie.
117. Populating Next Right Pointers in Each Node II
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This problem requires us to point the next of the left node in each layer to the right node. Because it is processed layer by layer, it is very intuitive to think of using BFS to solve it.
116. Populating Next Right Pointers in Each Node
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This problem requires us to point the next of the left node in each layer to the right node. Because it is processed layer by layer, it is very intuitive to think of using BFS to solve it.
1376. Time Needed to Inform All Employees
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After reading the problem at the beginning, you can probably feel that DFS should be used to solve it. Use DFS to calculate the sum of each inform time from headID to a leaf, and finally take the maximum time.
547. Number of Provinces
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The idea to solve this problem is to group connected nodes. The first thought is that we can use Union Find to group nodes.
200. Number of Islands
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The idea to solve this problem is to use DFS or BFS to visit adjacent lands for each unvisited land.
Union Find
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Union Find data structure is also known as disjoint set data structure. It is a data structure which stores a collection of disjoint sets. It provides two operations, one for merging two sets and one for finding the set with a given element.
Android Looper and Handler Tutorial
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Looper and Handler are one of the Android core components, and many high-level components are built on top of them. Understanding them helps us understand how some core components work. This article will introduce Looper and Handler and related components.
