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Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. k is a positive integer and is less than or equal to 阅读全文
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Given a linked list, rotate the list to the right by k places, where k is non-negative. Example 1: Example 2: 与189. Rotate Array 类似，但链表不能通过index来访问，要一 阅读全文
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The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return the 阅读全文
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The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all 阅读全文
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Validate if a given string can be interpreted as a decimal number. Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => true" 阅读全文
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Given a string containing only digits, restore it by returning all possible valid IP address combinations. Example: 解法：Backtracking Java: Java: Java: 阅读全文
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Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only 阅读全文
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Add a third dimension of time to a hashmap , so ur hashmap will look something like this - HashMap<K, t, V> where t is a float value. Implement the ge 阅读全文