A tree is a acyclic, connected graph. graph-valid-tree
Detecting a cycle in a graph efficiently requires two stacks. One for current path. The other for completed path.
- course-schedule
- https://www.geeksforgeeks.org/detect-and-remove-loop-in-a-linked-list/
- https://segmentfault.com/a/1190000003817671
- https://blog.csdn.net/monkeyduck/article/details/50439840
- https://hk.saowen.com/a/cba7ebff25749dd32c100b62e45637ef087ce8102227d59b86fc3fb8c9562203
- https://www.jianshu.com/p/9b6a9bf31144
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https://leetcode.com/problems/find-all-anagrams-in-a-string/
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https://leetcode.com/problems/longest-substring-without-repeating-characters/
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https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/
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https://leetcode.com/problems/substring-with-concatenation-of-all-words/
- LeetCode 刷题指南（一）
- leetcode 刷题指南
- A general approach to backtracking questions in Java (Subsets, Permutations, Combination Sum, Palindrome Partioning
- https://medium.com/@sourabreddy
- https://github.com/hanzichi/leetcode
- https://my.oschina.net/cofama
- https://github.com/jeantimex/javascript-problems-and-solutions