LouisLan的学习简记 👋🏼

题目地址 https://leetcode.com/problems/sort-colors/ 题目描述 Given an array with n objects colored red, white or blue, sort them **in-place **so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively. Note: You are not suppose to use the library's sort function for this problem. Example: Input: [2,0,2,1,1,0] Output: [0,0,1,1,2,2] Follow up: A rather straight forwa....

题目地址 https://leetcode.com/problems/search-a-2d-matrix/ 题目描述 Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right. The first integer of each row is greater than the last integer of the previous row. Example 1: Input: matrix = [ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50] ] target = 3 Output: true Example 2: Input: matrix = [ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50] ] ....

题目地址 https://leetcode.com/problems/set-matrix-zeroes/ 题目描述 Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place. Example 1: Input: [ [1,1,1], [1,0,1], [1,1,1] ] Output: [ [1,0,1], [0,0,0], [1,0,1] ] Example 2: Input: [ [0,1,2,0], [3,4,5,2], [1,3,1,5] ] Output: [ [0,0,0,0], [0,4,5,0], [0,3,1,0] ] Follow up: A straight forward solution using O(m**n) space is probably a bad idea. A simple improvement uses O(m + n) space, but still not the best solution. Coul....

题目地址 https://leetcode.com/problems/edit-distance/ 题目描述 Given two words word1 and word2 , find the minimum number of operations required to convert word1 to word2. You have the following 3 operations permitted on a word: Insert a character Delete a character Replace a character Example 1: Input: word1 = "horse", word2 = "ros" Output: 3 Explanation: horse -> rorse (replace 'h' with 'r') rorse -> rose (remove 'r') rose -> ros (remove 'e') Example 2: Input: word1 = "intention", word2 = "....

题目地址 https://leetcode.com/problems/simplify-path/ 题目描述 Given an absolute path for a file (Unix-style), simplify it. Or in other words, convert it to the canonical path. In a UNIX-style file system, a period . refers to the current directory. Furthermore, a double period .. moves the directory up a level. For more information, see: Absolute path vs relative path in Linux/Unix Note that the returned canonical path must always begin with a slash /, and there must be only a single slash / between tw....

题目地址 https://leetcode.com/problems/climbing-stairs/ 题目描述 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 integer. Example 1: Input: 2 Output: 2 Explanation: There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps Example 2: Input: 3 Output: 3 Explanation: There are three ways to climb to the top. 1. 1 step + 1 step + 1 step 2. 1 ste....

题目地址 https://leetcode.com/problems/sqrtx/ 题目描述 Implement int sqrt(int x). Compute and return the square root of x, where x is guaranteed to be a non-negative integer. Since the return type is an integer, the decimal digits are truncated and only the integer part of the result is returned. Example 1: Input: 4 Output: 2 Example 2: Input: 8 Output: 2 Explanation: The square root of 8 is 2.82842..., and since the decimal part is truncated, 2 is returned. 思路 这道题要求我们求平方根，我们能想到的方法就是算一个候选值的平方，然后和 x 比较大小....

题目地址 https://leetcode.com/problems/text-justification/ 题目描述 Given an array of words and a width maxWidth , format the text such that each line has exactly maxWidth characters and is fully (left and right) justified. You should pack your words in a greedy approach; that is, pack as many words as you can in each line. Pad extra spaces ' ' when necessary so that each line has exactly maxWidth characters. Extra spaces between words should be distributed as evenly as possible. If the number of spaces....

题目地址 https://leetcode.com/problems/add-binary/ 题目描述 Given two binary strings, return their sum (also a binary string). The input strings are both non-empty and contains only characters 1 or 0. Example 1: Input: a = "11", b = "1" Output: "100" Example 2: Input: a = "1010", b = "1011" Output: "10101" 思路 二进制数相加，并且保存在 string 中，要注意的是如何将 string 和 int 之间互相转换，并且每位相加时，会有进位的可能，会影响之后相加的结果。而且两个输入 string 的长度也可能会不同。这时我们需要新建一个 string，它的长度是两条输入 string 中的较大的那个，并且把较短的那个输入 string 通过在开头加字符‘0’来补的较大的那个长度。这时候我们逐个从两个 s....

题目地址 https://leetcode.com/problems/plus-one/ 题目描述 Given a non-empty array of digits representing a non-negative integer, plus one to the integer. The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit. You may assume the integer does not contain any leading zero, except the number 0 itself. Example 1: Input: [1,2,3] Output: [1,2,4] Explanation: The array represents the integer 123. Example 2: Input: [4,3,2,1] Ou....