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606. Construct String from Binary Tree You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traver 阅读全文
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104. Maximum Depth of Binary Tree Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from th 阅读全文
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669. Trim a Binary Search Tree Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lie 阅读全文
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122. Best Time to Buy and Sell Stock II Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to 阅读全文
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总结Hashmap和Hashtable的区别 阅读全文
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617. Merge Two Binary Trees 递归！递归！ 阅读全文
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283. Move Zeroes Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements. 阅读全文
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448. Find All Numbers Disappeared in an Array Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others 阅读全文
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234. Palindrome Linked List Given a singly linked list, determine if it is a palindrome. 阅读全文
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160. Intersection of Two Linked Lists Write a program to find the node at which the intersection of two singly linked lists begins. For example, the f 阅读全文