Davey的专栏

Leetcode–14. Longest Common Prefix本题比较简单，对字符串进行纵向扫描即可，从位置0开始，直到遇到一个不匹配。注意考虑字符串为空的情况，否则不能AC。C++代码如下：string longestCommonPrefix(vector<string>& strs) { if(strs.empty()) return "";

题目：Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock),

题目：Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. The Sudoku board could be partially filled, where empty cells are filled with the character ‘.’. A partially filled sud

题目：Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy on

题目：Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.Example:Input: "babad"Output: "bab"Note: "aba" is also a valid answer.Example:Inp

题目：Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array[-2,1,-3,4,-1,2,1,-5,4], the contiguous subarray [4,-1,2,1] has t

题目：Follow up for “Unique Paths”: Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid

题目：A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the

题目：Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down or right at a

题目：You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?Note: Given n will be a positive

题目：Given n, how many structurally unique BST’s (binary search trees) that store values 1…n?For example, Given n = 3, there are a total of 5 unique BST’s. 1 3 3 2 1 \

题目：Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) -> 1sumRange(2, 5) -> -1sumRange(0, 5) -> -3No

题目：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 you from robbing each of them is that adjacent hou

题目：After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all houses at this place are arranged in a

题目：Initially on a notepad only one character ‘A’ is present. You can perform two operations on this notepad for each step:Copy All: You can copy all the characters present on the notepad (partial copy

题目：Given a non-negative integer represented as a non-empty array of digits, plus one to the integer. You may assume the integer do not contain any leading zero, except the number 0 itself. The digits

题目：Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note: You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additio

题目：Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [2], [3,4], [6,5,7]

题目：Given an integer array, your task is to find all the different possible increasing subsequences of the given array, and the length of an increasing subsequence should be at least 2 . Example:Input:

题目：Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exact

题目：Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is given below.Input:Digit string “2

题目：Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. For example, given n = 3, a solution set is:[ "((()))", "(()())", "(())()", "()(())",

题目：Given a linked list, remove the nth node from the end of list and return its head.For example,Given linked list: 1->2->3->4->5, and n = 2.After removing the second node from the end, the linked list

题目：Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.The brackets must close in the correct order, “()” and “()[]{}” are all valid bu

题目：Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.思路： 本题考查基础的链表操作。因为两个链表l1和l2已经有序，所以只需要按顺序比较即可，把较小的结点插入到新的

题目：The count-and-say sequence is the sequence of integers beginning as follows: 1, 11, 21, 1211, 111221, ...1 is read off as “one 1” or 11. 11 is read off as “two 1s” or 21. 21 is read off as “one 2

题目：Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.Do not allocate extra space for another array, you must do this in place with c

题目：Given an array and a value, remove all instances of that value in place and return the new length.Do not allocate extra space for another array, you must do this in place with constant memory.The or

题目：Implement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.思路：本题是让找到一个字符串是不是另一个字符串的子串，如果是就返回下标，如果不是返回-1。暴力比较，时间复杂度：O(mn)。C++代码如下：int

题目：Divide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.思路：不用乘法，除法和取模运算实现两个数的除法。注意考虑边界，如果divisor = -1, dividend = INT_MIN这时候会产生溢出，直接返回INT_MAX。

题目：Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rearrange it as the lowest possible o

题目：Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).You are given a target value to search. If found in the

题目：Given an array of integers sorted in ascending order, find the starting and ending position of a given target value.Your algorithm’s runtime complexity must be in the order of O(log n).If the target

题目：Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant space. You may n

题目：Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. You may assume no duplicates in the array.

题目：Given numRows, generate the first numRows of Pascal’s triangle. For example, given numRows = 5, Return[ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]]思路： 本题主要考查vector 的基本操作，杨辉三角形的计算