随笔分类 - LeetCode
摘要：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 order (ie, sorted in ascending order).The replacement must be in-place, do not allocate extra memory.He
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摘要：The set[1,2,3,…,n]contains a total ofn! unique permutations.By listing and labeling all of the permutations in order,We get the following sequence (ie, forn= 3):"123""132""213""231""312""321"Givennandk, return thekthpermutation sequence.Not
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摘要：Given a collection of numbers that might contain duplicates, return all possible unique permutations.For example,[1,1,2]have the following unique permutations:[1,1,2],[1,2,1], and[2,1,1].Solution:由于数据中有重复，在递归时需要判断是否可以交换。基本的枚举思路是每个数分别出现在第k位，然后排列剩下的元素。这里第k位的元素在枚举过程中需要判断是否已经出现过。class Solution {public:
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摘要：Given a collection of numbers, return all possible permutations.For example,[1,2,3]have the following permutations:[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2], and[3,2,1].Solution:对一个没有重复元素的序列做全排序，可以考虑采用递归的思路。n个元素的全排列为n个元素分别作为第一个元素，并加上分别去除首元素剩下元素的全排列。当序列递归到只有一个元素时，递归终止，一个可行的全排列产生。class Solution {public:
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摘要：Mergeksorted linked lists and return it as one sorted list. Analyze and describe its complexity.Soluton:/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public: ListNode *mergeKLi...
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摘要：Given a string, determine if it is a palindrome, considering only alphanumeric(字母与数字) characters and ignoring cases.For example,"A man, a plan, a canal: Panama"is a palindrome.（不区分大小写）"race a car"isnota palindrome.Note:Have you consider that the string might be empty? This is a g
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摘要：Given a linked list, return the node where the cycle begins. If there is no cycle, returnnull.Follow up:Can you solve it without using extra space?Solution:首先选取一快一慢两个指针fast与slow: fast每步走两个结点，slow每步走一个结点。若链表有环，则fast将会在某一个时刻追上slow。1. 假设链表有环，且链表长度为n，循环从第k + 1个结点开始(亦即走k步进入循环)2. 让两个指针fast, slow从链表头同时开始遍历
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摘要：Sort a linked list using insertion sort.Solution:新建链表，逐个插入即可~/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public: ListNode *insertionSortList(ListNode *head) { if(head ...
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摘要：Evaluate the value of an arithmetic expression inReverse Polish Notation.Valid operators are+,-,*,/. Each operand may be an integer or another expression.Some examples:["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9["4", "13"
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摘要：Given an input string, reverse the string word by word.For example,Given s = "the sky is blue",return "blue is sky the".click to show clarification.Clarification:What constitutes a word?A sequence of non-space characters constitutes a word.Could the input string contain leading o
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摘要：There areNgas stations along a circular route, where the amount of gas at stationiisgas[i].You have a car with an unlimited gas tank and it costscost[i]of gas to travel from stationito its next station (i+1). You begin the journey with an empty tank at one of the gas stations.Return the starting gas
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摘要：The string"PAYPALISHIRING"is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P A H NA P L S I I GY I RAnd then read line by line:"PAHNAPLSIIGYIR"Write the code that will take a string and
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摘要：You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.Input:(2 -> 4 -> 3) + (5 -> 6 -> 4)Output:7 -> 0 -> 8Solutions:/** * Defin
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摘要：Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Your goal is to reach the last index in the minimum number of jumps.For example:Given array A =[2,3,1,1,4]The minimum n
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摘要：Write a function to find the longest common prefix string amongst an array of strings.Solution:class Solution {public: string longestCommonPrefix(vector &strs) { int len = 0, n = strs.size(), MaxL = 0; if(n == 0) return ""; else if(n == 1) return strs[0]; for(i...
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摘要：Given a linked list and a valuex, partition it such that all nodes less thanxcome before nodes greater than or equal tox.You should preserve the original relative order of the nodes in each of the two partitions.For example,Given1->4->3->2->5->2andx= 3,return1->2->2->4->3-
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摘要：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], [4,1,8,3]]The minimum path sum from top to bottom is11(i.e.,2+3+5+1= 11).Note:Bonus point if you are a...
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摘要：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 as1and0respectively in the grid.For example,There is one obstacle in the middle of a 3x3 grid as illustrated below.[ [0,0,0], [0,1,
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摘要：Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Determine if you are able to reach the last index.For example:A =[2,3,1,1,4], returntrue.A =[3,2,1,0,4], returnfalse.So
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摘要：Given an unsorted array of integers, find the length of the longest consecutive elements sequence.For example,Given[100, 4, 200, 1, 3, 2],The longest consecutive elements sequence is[1, 2, 3, 4]. Return its length:4.Your algorithm should run in O(n) complexity.Solution:class Solution {public: set...
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