原文链接: https://leetcode-cn.com/problems/is-unique-lcci 英文原文Implement an algorithm to determine if a string has all unique characters. What if you cannot use additional data structures? Example 1: Input: s = "leetcode" Output: false Example 2: Input: s…

原文链接: https://leetcode-cn.com/problems/check-permutation-lcci 英文原文Given two strings,write a method to decide if one is a permutation of the other. Example 1: Input: s1 = "abc", s2 = "bca" Output: true Example 2: Input: s1 = "abc", s2 = "bad" Output: …

原文链接: https://leetcode-cn.com/problems/string-to-url-lcci 英文原文Write a method to replace all spaces in a string with '%20'. You may assume that the string has sufficient space at the end to hold the additional characters,and that you are given the "tr…

原文链接: https://leetcode-cn.com/problems/compress-string-lcci 英文原文Implement a method to perform basic string compression using the counts of repeated characters. For example, the string aabcccccaaa would become a2blc5a3. If the "compressed" string woul…

原文链接: https://leetcode-cn.com/problems/string-rotation-lcci 英文原文Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 (e.g.,"waterbottle" is a rotation of"erbottlewat"). Can you use only one call to the method that checks if one…

原文链接: https://leetcode-cn.com/problems/remove-duplicate-node-lcci 英文原文Write code to remove duplicates from an unsorted linked list. Example1: Input: [1, 2, 3, 3, 2, 1] Output: [1, 2, 3] Example2: Input: [1, 1, 1, 1, 2] Output: [1, 2] Note: The length…

原文链接: https://leetcode-cn.com/problems/palindrome-linked-list-lcci 英文原文Implement a function to check if a linked list is a palindrome. Example 1: Input: 1->2 Output: false Example 2: Input: 1->2->2->1 Output: true Follow up: Could you do it in O(n) t…

原文链接: https://leetcode-cn.com/problems/intersection-of-two-linked-lists-lcci 英文原文Given two (singly) linked lists, determine if the two lists intersect. Return the inter­ secting node. Note that the intersection is defined based on reference, not …

原文链接: https://leetcode-cn.com/problems/min-stack-lcci 英文原文How would you design a stack which, in addition to push and pop, has a function min which returns the minimum element? Push, pop and min should all operate in 0(1) time. Example: MinStack minS…

原文链接: https://leetcode-cn.com/problems/implement-queue-using-stacks-lcci 英文原文Implement a MyQueue class which implements a queue using two stacks. Example: MyQueue queue = new MyQueue(); queue.push(1); queue.push(2); queue.peek(); // return 1 queue.po…

原文链接: https://leetcode-cn.com/problems/route-between-nodes-lcci 英文原文Given a directed graph, design an algorithm to find out whether there is a route between two nodes. Example1: Input: n = 3, graph = [[0, 1], [0, 2], [1, 2], [1, 2]], start = 0, targe…

原文链接: https://leetcode-cn.com/problems/three-in-one-lcci 英文原文Describe how you could use a single array to implement three stacks. You should implement push(stackNum, value)、pop(stackNum)、isEmpty(stackNum)、peek(stackNum) methods. stackNum is the index…

原文链接: https://leetcode-cn.com/problems/sort-of-stacks-lcci 英文原文Write a program to sort a stack such that the smallest items are on the top. You can use an additional temporary stack, but you may not copy the elements into any other data structure (su…

原文链接: https://leetcode-cn.com/problems/minimum-height-tree-lcci 英文原文Given a sorted (increasing order) array with unique integer elements, write an algo­rithm to create a binary search tree with minimal height. Example: Given sorted array: [-10,-3…

原文链接: https://leetcode-cn.com/problems/list-of-depth-lcci 英文原文Given a binary tree, design an algorithm which creates a linked list of all the nodes at each depth (e.g., if you have a tree with depth D, you'll have D linked lists). Return a array cont…

原文链接: https://leetcode-cn.com/problems/check-balance-lcci 英文原文Implement a function to check if a binary tree is balanced. For the purposes of this question, a balanced tree is defined to be a tree such that the heights of the two subtrees of any node…

原文链接: https://leetcode-cn.com/problems/legal-binary-search-tree-lcci 英文原文Implement a function to check if a binary tree is a binary search tree. Example 1: Input: 2 / \ 1 3 Output: true Example 2: Input: 5 / \ 1 4 / \ 3 6 Output: false Explanation: I…

原文链接: https://leetcode-cn.com/problems/successor-lcci 英文原文Write an algorithm to find the "next" node (i.e., in-order successor) of a given node in a binary search tree. Return null if there's no "next" node for the given node. Example 1: Input: root …

原文链接: https://leetcode-cn.com/problems/linked-list-cycle-lcci 英文原文Given a circular linked list, implement an algorithm that returns the node at the beginning of the loop. Circular linked list: A (corrupt) linked list in which a node's next pointer po…

原文链接: https://leetcode-cn.com/problems/first-common-ancestor-lcci 英文原文Design an algorithm and write code to find the first common ancestor of two nodes in a binary tree. Avoid storing additional nodes in a data structure. NOTE: This is not necessaril…

原文链接: https://leetcode-cn.com/problems/insert-into-bits-lcci 英文原文You are given two 32-bit numbers, N and M, and two bit positions, i and j. Write a method to insert M into N such that M starts at bit j and ends at bit i. You can assume that the bits …

原文链接: https://leetcode-cn.com/problems/exchange-lcci 英文原文Write a program to swap odd and even bits in an integer with as few instructions as possible (e.g., bit 0 and bit 1 are swapped, bit 2 and bit 3 are swapped, and so on). Example1: Input: num = …

原文链接: https://leetcode-cn.com/problems/convert-integer-lcci 英文原文Write a function to determine the number of bits you would need to flip to convert integer A to integer B. Example1: Input: A = 29 (0b11101), B = 15 (0b01111) Output: 2 Example2: Input: …

原文链接: https://leetcode-cn.com/problems/closed-number-lcci 英文原文Given a positive integer, print the next smallest and the next largest number that have the same number of 1 bits in their binary representation. Example1: Input: num = 2 (0b10) Output: [4…

原文链接: https://leetcode-cn.com/problems/palindrome-permutation-lcci 英文原文Given a string, write a function to check if it is a permutation of a palindrome. A palindrome is a word or phrase that is the same forwards and backwards. A permutation is a rear…

原文链接: https://leetcode-cn.com/problems/rotate-matrix-lcci 英文原文Given an image represented by an N x N matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees. Can you do this in place? Example 1: Given matrix…

原文链接: https://leetcode-cn.com/problems/zero-matrix-lcci 英文原文Write an algorithm such that if an element in an MxN matrix is 0, its entire row and column are set to 0. Example 1: Input: [ [1,1,1], [1,0,1], [1,1,1] ] Output: [ [1,0,1], [0,0,0], [1,0,1] …

原文链接: https://leetcode-cn.com/problems/sum-lists-lcci 英文原文You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored in reverse order, such that the 1's digit is at the head of the list. Write a …

原文链接: https://leetcode-cn.com/problems/stack-of-plates-lcci 英文原文Imagine a (literal) stack of plates. If the stack gets too high, it might topple. Therefore, in real life, we would likely start a new stack when the previous stack exceeds some threshol…

原文链接: https://leetcode-cn.com/problems/draw-line-lcci 英文原文A monochrome screen is stored as a single array of int, allowing 32 consecutive pixels to be stored in one int. The screen has width w, where w is divisible by 32 (that is, no byte will be spl…