摘要： 注意The loop must be "forward" or "backward'. 所以这就是为什么[-2, 1, -1, -2, -2]是false的原因 Just think it as finding a loop in Linkedlist, except that loops with 阅读全文

摘要： Topological Sort: This problem is to determine if there's one, and only one sequence to sort a DAG. The method is to check if the queue's size is alwa 阅读全文

摘要： My First Solution: Use Stack and String operation, from the back of the string, find the first '?', push the right to stack. Depends on whether the ch 阅读全文

摘要： Backtracking + Trie: referred to https://discuss.leetcode.com/topic/63516/explained-my-java-solution-using-trie-126ms-16-16 A better approach is to ch 阅读全文