2018年2月28日
摘要：
Find the sum of all left leaves in a given binary tree. 思路：在递归的时候访问左右节点记录一下，比如做节点标记1，右节点标2，那么当遍历到叶子节点的时候，我们只加标记为1的叶子节点的值。 阅读全文
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Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For exa 阅读全文
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You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality c 阅读全文
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Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. 前缀和思想。如果修改的次数比较多，那么就可以用线段树了, class NumArray { pu 阅读全文
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Given an integer, write a function to determine if it is a power of three. 判断一个数，是不是3的n次幂。直接换底公式求解 阅读全文
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Given two arrays, write a function to compute their intersection. Example: Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2]. Note: Each eleme 阅读全文
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Calculate the sum of two integers a and b, but you are not allowed to use the operator + and . Example: Given a = 1 and b = 2, return 3. 不用加减法进行求和运算。 阅读全文
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Write a function to delete a node (except the tail) in a singly linked list, given only access to that node. Supposed the linked list is 1 2 3 4 and y 阅读全文
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Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built in library functio 阅读全文
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Given a singly linked list, determine if it is a palindrome. Follow up: Could you do it in O(n) time and O(1) space? 判断一个链表是不是回文的。 思路：遍历节点得到总数tot，然后反转 阅读全文
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Implement the following operations of a queue using stacks. push(x) Push element x to the back of queue. pop() Removes the element from in front of qu 阅读全文
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Implement the following operations of a stack using queues. push(x) Push element x onto stack. pop() Removes the element on top of the stack. top() Ge 阅读全文
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Reverse a singly linked list. 思路：递归，每次保存一下上一个节点用来构造反转后的链表。 非递归，需要多记录两个值. 阅读全文
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Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrenc 阅读全文
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Remove all elements from a linked list of integers that have value val. 思路：声明两指针，类似快慢指针，快指针遇到val时跳过，直到值不是val这时修改慢指针的next为快指针，慢指针移到快指针这个位置。 阅读全文
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You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping yo 阅读全文
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Reverse bits of a given 32 bits unsigned integer. For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), retur 阅读全文
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Given a Binary Search Tree (BST) with the root node root, return the minimum difference between the values of any two different nodes in the tree. Not 阅读全文
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Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive intege 阅读全文
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Given two strings s and t which consist of only lowercase letters. String t is generated by random shuffling string s and then add one more letter at 阅读全文