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Topological sort is an basic topic in graph theory, which is the foundation for many other problems like calculating strongly connected components (SCC). This article will discuss a couple of problems related to topological sort and its application. I will

Problems about removing some characters in a string to make it lexicographically smallestThere are a bunch of problems in Leetcode about removing some characters / digits in a string to make it lexicographically smallest. Here i will have a discussion abo