Implement regular expression matching with support for '.' and '*'. '.' Matches any single character. '*' Matches zero or more of the preceding element. The matching should cover the entire input string (not partial). The function prototype should be…

Regular Expression Matching Implement regular expression matching with support for '.' and '*'. '.' Matches any single character. '*' Matches zero or more of the preceding element. The matching should cover the entire input string (not partial). The…

正则表达式的匹配,还是挺难的.可根据下一个字符是不是*分为两种情况处理,需要考虑多种情况. bool isMatch(const char *s, const char *p) { if (*p == '\0')return *s == '\0'; //如果下一个不是*(*可表示前一个字符的数量) //要么当前字符匹配,要么是.,不可跳过 ) != '*') { if (*s == *p || (*p == '.' && *s != '\0')) , p + ); else return…

最近代码写的少了,而leetcode一直想做一个python,c/c++解题报告的专题,c/c++一直是我非常喜欢的,c语言编程练习的重要性体现在linux内核编程以及一些大公司算法上机的要求,python主要为了后序转型数据分析和机器学习,所以今天来做一个难度为hard 的简单正则表达式匹配. 做了很多leetcode题目,我们来总结一下套路: 首先一般是检查输入参数是否正确,然后是处理算法的特殊情况,之后就是实现逻辑,最后就是返回值. 当编程成为一种解决问题的习惯,我们就成为了一名纯粹的程序…

写在前面   老粉丝可能知道现阶段的LeetCode刷题将按照某一个特定的专题进行,之前的[贪心算法]已经结束,虽然只有三个题却包含了简单,中等,困难这三个维度,今天介绍的是第二个专题[数组] 数组(Array)是一种线性表数据结构.它用一组连续的内存空间,来存储一组具有相同类型的数据.在每一种编程语言中,基本都会有数组这种数据类型.不过,它不仅仅是一种编程语言中的数据类型,还是一种最基础的数据结构. 贪心算法回顾: [LeetCode]贪心算法--买卖股票的最佳时机II(122) [LeetC…

[题意] 给两个字符串s和p,判断s是否能用p进行匹配. [题解] dp[i][j]表示s的前i个是否能被p的前j个匹配. 首先可以分成3大类情况,我们先从简单的看起: (1)s[i - 1] = p[j - 1],易得dp[i][j] = dp[i-1][j-1] (2)p[i - 1] = '.',因为'.'可以匹配任何字符,所以dp[i][j] = dp[i-1][j-1] (3)p[i - 1] = '*',这种情况就比较复杂了. 当p[j - 2] != s[i - 1] &&…

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by…

题目链接 https://leetcode.com/problems/regular-expression-matching/?tab=Description   '.' Matches any single character.匹配任何单字符 '*' Matches zero or more of the preceding element.匹配0个或者多个前置元素 采用动态规划方法 public boolean isMatch(String s, String p) 1, If p.char…

描述 Given a collection of distinct integers, return all possible permutations. Example: Input: [1,2,3] Output: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ] 思路一:递归 利用STL的函数swap()来交换数组的元素 class Solution { public: vector<vector<int>> p…

1. Description Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array. Formally the function should: Return true if there exists i, j, k such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤…

1. Description The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized tha…

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Ensure that numbers within the set are sorted in ascending order. Example 1…

Sort a linked list using insertion sort. 思路: 用插入排序对链表排序.插入排序是指每次在一个排好序的链表中插入一个新的值. 注意:把排好序的部分和未排序的部分完全分开,指针不要有交叉. 即不会通过->next 重叠 class Solution { public: ListNode *insertionSortList(ListNode *head) { if(head == NULL) return NULL; ListNode * ans = hea…

Reverse a singly linked list. 思路:没啥好说的.秒... ListNode* reverseList(ListNode* head) { ListNode * rList = NULL, * tmp = NULL; while(head != NULL) { tmp = rList; rList = head; head = head->next; rList->next = tmp; } return rList; }…

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA. Write a function to find all the 10-letter-long seq…

Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. 思路: 我居然在这道题上卡了一个小时.关键是对于平衡的定义,我开始理解…

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. 思路:不能用额外空间,就用矩阵的第一行和第一列来标记这一行或这一列是否需要置0. 用两个bool量记录第一行和第一列是否需要置0 大神的代码和我的代码都是这个思路,但是我在画0的时候是行列分开处理的,大神的代码是一起处理的 void setZeroes(vector<vector<int> > &…

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example,Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ] 思路: 我是直接套用了Spiral Matrix 的代码 class Solution { p…

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. Here are few examples.[1,3,5,6], 5 → 2[1,3,5,6], 2 →…

Given an array of integers, every element appears three times except for one. Find that single one. Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 自己不会做... 搜答案,发现思路真是太巧妙了 关键:统计每一位上出现1的次…

Compare two version numbers version1 and version2.If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0. You may assume that the version strings are non-empty and contain only digits and the . character.The . characte…

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, then one 1" or 1211. Given an…

Given an integer n, return the number of trailing zeroes in n!. Note: Your solution should be in logarithmic time complexity. 思路:编程之美里有,就是找因子5的个数. int trailingZeroes(int n) { ; ) { ans += n / ; n /= ; } return ans; }…

Divide two integers without using multiplication, division and mod operator. If it is overflow, return MAX_INT. 思路: 尼玛,各种通不过,开始用纯减法,超时了. 然后用递归,溢出了. 再然后终于开窍了,用循环,把被除数每次加倍去找答案,结果一遇到 -2147483648 就各种不行, 主要是这个数一求绝对值就溢出了. 再然后,受不了了,看答案. 发现,大家都用long long来解决溢…

Write a function to find the longest common prefix string amongst an array of strings. 思路:找最长公共前缀 常规方法 string longestCommonPrefix(vector<string> &strs) { ) return ""; ) ]; string ans; ; ) { ; i < strs.size(); i++) { ].size() <= n…

Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that: Only one letter can be changed at a time Each intermediate word must exist in the dictionary For example, Given:start = "hit…

Single Number 题目 Given an array of integers, every element appears twice except for one. Find that single one.      Note:      Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 思路: 为了满足时间和空间复杂度…

Search Insert Position 意: 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. Here are few examples.  [1…

Problem:You are given an array x of n positive numbers. You start at point (0,0) and moves x[0] metres to the north, then x[1] metres to the west, x[2] metres to the south,x[3] metres to the east and so on. In other words, after each move your direct…

[10]Regular Expression Matching [17]Letter Combinations of a Phone Number [22]Generate Parentheses (2019年2月13日) 给了一个N,生成N对括号的所有情况的字符串. n = 3 [ "((()))", "(()())", "(())()", "()(())", "()()()" ] 题解:dfs生成. c…