原文链接: https://leetcode-cn.com/problems/three-steps-problem-lcci 英文原文A child is running up a staircase with n steps and can hop either 1 step, 2 steps, or 3 steps at a time. Implement a method to count how many possible ways the child can run up the s…

原文链接: https://leetcode-cn.com/problems/power-set-lcci 英文原文Write a method to return all subsets of a set. The elements in a set are pairwise distinct. Note: The result set should not contain duplicated subsets. Example: Input: nums = [1,2,3] Output: […

原文链接: https://leetcode-cn.com/problems/recursive-mulitply-lcci 英文原文Write a recursive function to multiply two positive integers without using the * operator. You can use addition, subtraction, and bit shifting, but you should minimize the number of t…

原文链接: https://leetcode-cn.com/problems/bracket-lcci 英文原文Implement an algorithm to print all valid (e.g., properly opened and closed) combinations of n pairs of parentheses. Note: The result set should not contain duplicated subsets. For example, give…

原文链接: https://leetcode-cn.com/problems/color-fill-lcci 英文原文Implement the "paint fill" function that one might see on many image editing programs. That is, given a screen (represented by a two-dimensional array of colors), a point, and a new color, fi…

原文链接: https://leetcode-cn.com/problems/pile-box-lcci 英文原文You have a stack of n boxes, with widths wi, depths di, and heights hi. The boxes cannot be rotated and can only be stacked on top of one another if each box in the stack is strictly larger tha…

原文链接: https://leetcode-cn.com/problems/bianry-number-to-string-lcci 英文原文Given a real number between 0 and 1 (e.g., 0.72) that is passed in as a double, print the binary representation. If the number cannot be represented accurately in binary with at …

原文链接: https://leetcode-cn.com/problems/check-subtree-lcci 英文原文T1 and T2 are two very large binary trees. Create an algorithm to determine if T2 is a subtree of T1. A tree T2 is a subtree of T1 if there exists a node n in T1 such that the subtree of n…

原文链接: https://leetcode-cn.com/problems/reverse-bits-lcci 英文原文You have an integer and you can flip exactly one bit from a 0 to a 1. Write code to find the length of the longest sequence of 1s you could create. Example 1: Input: num = 1775(110111011112…

原文链接: https://leetcode-cn.com/problems/coin-lcci 英文原文Given an infinite number of quarters (25 cents), dimes (10 cents), nickels (5 cents), and pennies (1 cent), write code to calculate the number of ways of representing n cents. (The result may be la…

原文链接: https://leetcode-cn.com/problems/search-rotate-array-lcci 英文原文Given a sorted array of n integers that has been rotated an unknown number of times, write code to find an element in the array. You may assume that the array was originally sorted i…

原文链接: https://leetcode-cn.com/problems/eight-queens-lcci 英文原文Write an algorithm to print all ways of arranging n queens on an n x n chess board so that none of them share the same row, column, or diagonal. In this case, "diagonal" means all diagonals…

原文链接: https://leetcode-cn.com/problems/magic-index-lcci 英文原文A magic index in an array A[0...n-1] is defined to be an index such that A[i] = i. Given a sorted array of integers, write a method to find a magic index, if one exists, in array A. If not, …

原文链接: https://leetcode-cn.com/problems/permutation-i-lcci 英文原文Write a method to compute all permutations of a string of unique characters. Example1: Input: S = "qwe" Output: ["qwe", "qew", "wqe", "weq", "ewq", "eqw"] Example2: Input: S = "ab" Output:…

原文链接: https://leetcode-cn.com/problems/sparse-array-search-lcci 英文原文Given a sorted array of strings that is interspersed with empty strings, write a method to find the location of a given string. Example1: Input: words = ["at", "", "", "", "ball", ""…

原文链接: https://leetcode-cn.com/problems/swap-numbers-lcci 英文原文Write a function to swap a number in place (that is, without temporary variables). Example: Input: numbers = [1,2] Output: [2,1] Note: numbers.length == 2 -2147483647 <= numbers[i] <= 21474…

原文链接: https://leetcode-cn.com/problems/words-frequency-lcci 英文原文Design a method to find the frequency of occurrences of any given word in a book. What if we were running this algorithm multiple times? You should implement following methods: WordsFreq…

原文链接: https://leetcode-cn.com/problems/tic-tac-toe-lcci 英文原文Design an algorithm to figure out if someone has won a game of tic-tac-toe. Input is a string array of size N x N, including characters " ", "X" and "O", where " " represents a empty grid. T…

原文链接: https://leetcode-cn.com/problems/smallest-difference-lcci 英文原文Given two arrays of integers, compute the pair of values (one value in each array) with the smallest (non-negative) difference. Return the difference. Example: Input: {1, 3, 15, 11, …

原文链接: https://leetcode-cn.com/problems/yong-liang-ge-zhan-shi-xian-dui-lie-lcof 中文题目用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 ) 示例 1： 输入： ["CQueue","appendTail","deleteHead","deleteH…

原文链接: https://leetcode-cn.com/problems/fei-bo-na-qi-shu-lie-lcof 中文题目写一个函数，输入 n ，求斐波那契（Fibonacci）数列的第 n 项（即 F(N)）。斐波那契数列的定义如下： F(0) = 0, F(1) = 1 F(N) = F(N - 1) + F(N - 2), 其中 N > 1. 斐波那契数列由 0 和 1 开始，之后的斐波那契数就是由之前的两数相加而得出。 答案需要取模 1e9+7（1000000007），如…

原文链接: https://leetcode-cn.com/problems/shu-zu-zhong-zhong-fu-de-shu-zi-lcof 中文题目找出数组中重复的数字。 在一个长度为 n 的数组 nums 里的所有数字都在 0～n-1 的范围内。数组中某些数字是重复的，但不知道有几个数字重复了，也不知道每个数字重复了几次。请找出数组中任意一个重复的数字。 示例 1： 输入： [2, 3, 1, 0, 2, 5, 3] 输出：2 或 3 限制： 2 <= n <= 100000 通过…

原文链接: https://leetcode-cn.com/problems/er-wei-shu-zu-zhong-de-cha-zhao-lcof 中文题目在一个 n * m 的二维数组中，每一行都按照从左到右递增的顺序排序，每一列都按照从上到下递增的顺序排序。请完成一个高效的函数，输入这样的一个二维数组和一个整数，判断数组中是否含有该整数。 示例: 现有矩阵 matrix 如下： [ [1, 4, 7, 11, 15], [2, 5, 8, 12, 19], [3, 6, 9, 16, 2…

原文链接: https://leetcode-cn.com/problems/qing-wa-tiao-tai-jie-wen-ti-lcof 中文题目一只青蛙一次可以跳上1级台阶，也可以跳上2级台阶。求该青蛙跳上一个 n 级的台阶总共有多少种跳法。 答案需要取模 1e9+7（1000000007），如计算初始结果为：1000000008，请返回 1。 示例 1： 输入：n = 2 输出：2 示例 2： 输入：n = 7 输出：21 示例 3： 输入：n = 0 输出：1 提示： 0 <= n …

原文链接: https://leetcode-cn.com/problems/xuan-zhuan-shu-zu-de-zui-xiao-shu-zi-lcof 中文题目把一个数组最开始的若干个元素搬到数组的末尾，我们称之为数组的旋转。 给你一个可能存在 重复 元素值的数组 numbers ，它原来是一个升序排列的数组，并按上述情形进行了一次旋转。请返回旋转数组的最小元素。例如，数组 [3,4,5,1,2] 为 [1,2,3,4,5] 的一次旋转，该数组的最小值为1。 示例 1： 输入：[3,4…

原文链接: https://leetcode-cn.com/problems/ju-zhen-zhong-de-lu-jing-lcof 中文题目给定一个 m x n 二维字符网格 board 和一个字符串单词 word 。如果 word 存在于网格中，返回 true ；否则，返回 false 。 单词必须按照字母顺序，通过相邻的单元格内的字母构成，其中“相邻”单元格是那些水平相邻或垂直相邻的单元格。同一个单元格内的字母不允许被重复使用。 例如，在下面的 3×4 的矩阵中包含单词 "ABCCED…

原文链接: https://leetcode-cn.com/problems/ti-huan-kong-ge-lcof 中文题目请实现一个函数，把字符串 s 中的每个空格替换成"%20"。 示例 1： 输入：s = "We are happy." 输出："We%20are%20happy." 限制： 0 <= s 的长度 <= 10000 通过代码 高赞题解方法一：遍历添加在 Python 和 Java 等语言中，字符串都被设计成「不可变」的类型，即无法直接修改字符串的某一位字符，需要新建一个字…

原文链接: https://leetcode-cn.com/problems/cong-wei-dao-tou-da-yin-lian-biao-lcof 中文题目输入一个链表的头节点，从尾到头反过来返回每个节点的值（用数组返回）。 示例 1： 输入：head = [1,3,2] 输出：[2,3,1] 限制： 0 <= 链表长度 <= 10000 通过代码 高赞题解方法一：递归法解题思路： 利用递归： 先走至链表末端，回溯时依次将节点值加入列表 ，这样就可以实现链表值的倒序输出。 Python …

原文链接: https://leetcode-cn.com/problems/zhong-jian-er-cha-shu-lcof 中文题目输入某二叉树的前序遍历和中序遍历的结果，请构建该二叉树并返回其根节点。 假设输入的前序遍历和中序遍历的结果中都不含重复的数字。 示例 1: Input: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7] Output: [3,9,20,null,null,15,7] 示例 2: Input: preorder…

原文链接: https://leetcode-cn.com/problems/jian-sheng-zi-lcof 中文题目给你一根长度为 n 的绳子，请把绳子剪成整数长度的 m 段（m、n都是整数，n>1并且m>1），每段绳子的长度记为 k[0],k[1]...k[m-1] 。请问 k[0]*k[1]*...*k[m-1] 可能的最大乘积是多少？例如，当绳子的长度是8时，我们把它剪成长度分别为2、3、3的三段，此时得到的最大乘积是18。 示例 1： 输入: 2 输出: 1 解释: 2 = 1 …