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原创 475. Heaters

Question - Nested loop, time exceeded.- Binary search.- Note: whenever uses binary search, sort before search.public class Solution { public int findRadius(int[] houses, int[] heaters) {

2017-03-08 10:27:13 409

原创 [Leetcode] 506. Relative Ranks

QuestionFirst thought, copy array -> sort array -> reverse sorted array -> nested loop, outer loop go through sorted array, inner loop go through original array and assign value to result when ele

2017-02-21 01:42:07 442

原创 [LeetCode] 406. Queue Reconstruction by Height

1. Convert 2D array to people list2. Customize a Comparator to sort the people list, which ensure people with lower k should be in the front of the queue + in the case of same k for multiple people,

2016-11-04 09:07:11 499

原创 [LeetCode] 398. Random Pick Index

QUESTION1. Use a hash map > to store the input array2. Every time pick method invoke, get the list of index for given target number, get the random list index by rand.((max-min)+1)+minpublic cla

2016-10-27 09:19:47 339

原创 [LeetCode] 396. Rotate Function

QUESTIONO(n^2) approach:public class Solution { public int maxRotateFunction(int[] A) { if(A == null || A.length == 0){ return 0; } int max = Integ

2016-10-26 12:23:43 296

原创 [LeetCode] 395. Longest Substring with At Least K Repeating Characters

QUESTIONThought: Split string by the characters repeating less than k. Recursively call function with the sub string until sub string can not be split. Store the length of the longest un-split sub s

2016-10-25 09:46:09 307

原创 [LeetCode] 393. UTF-8 Validation

QUESTIONImplement rules one by one. Keep calm, be patient..public class Solution { public boolean validUtf8(int[] data) { if(data == null || data.length == 0){ return tr

2016-10-24 06:21:19 460

原创 [LeetCode] 392. Is Subsequence

Given a string s and a string t, check if s is subsequence of t.You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, a

2016-10-23 01:35:47 284

原创 [LeetCode] 390. Elimination Game

public class Solution { public int lastRemaining(int n) { if(n < 1){ return 0; } if(n==1){ return 1; } int gap =

2016-10-23 00:53:38 429

原创 [leet code] Pow(x, n)

Question: Implement pow(x, n).第二次做这道题仍然对以2为基数的解题方式感觉陌生. 直观做法, 超时. 于是只能考虑数值运算两大进阶解法:1. 两分法 O(logn)2. 2为基数: 将目标数字拆解成以2为基数的构成方式, 例如 123 = 2^6+2^5+2^4+2^3+2^1+2^0 O(logn)对于第二种解法:Step1: n为负数

2016-01-03 01:18:43 704

原创 [leet code] Edit Distance

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)You have the following 3 operations permitted on a word:

2014-02-22 03:15:12 3131

原创 [leet code] Next Permutation

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

2014-02-21 08:15:23 840

原创 [leet code] Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.For example,Given 1->2->3->3->4->4->5, return 1->2->5.Given 1->1-

2014-02-20 01:11:29 715

原创 [leet code] Palindrome Partitioning

Given a string s, partition s such that every substring of the partition is a palindrome.Return all possible palindrome partitioning of s.For example, given s = "aab",Return [ ["aa","

2014-02-19 23:07:28 911

原创 [leet code] Add Binary

Given two binary strings, return their sum (also a binary string).For example,a = "11"b = "1"Return "100".===========Analysis:Idea is to implement the manual calculation process. Whic

2014-02-14 07:56:35 793

原创 [leet code] Reverse Linked List II

Reverse a linked list from position m to n. Do it in-place and in one-pass.For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4,return 1->4->3->2->5->NULL.Note:Given m, n satisfy t

2014-02-14 00:37:43 2906

原创 [leet code] Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.============Analysis:Exact the same idea as [leet cod

2014-02-13 01:55:25 864

原创 [leet code] Construct Binary Tree from Inorder and Postorder Traversal

Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.=================A scary problem at the very beginning

2014-02-13 01:29:02 2080

原创 [leet code] Validate Binary Search Tree

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with keys less than the node's key.Th

2014-02-12 00:26:50 690

原创 [leet code] Letter Combinations of a Phone Number

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 st

2014-02-11 23:39:37 698

原创 [leet code] Insertion Sort List

Sort a linked list using insertion sort.=====================Analysis:Idea is to implement the insertion sort from array to linked list. Basic idea of insertion sort is that, examine array el

2014-02-11 03:42:12 1036

原创 [leet code] Unique Binary Search Trees II

Given n, generate all structurally unique BST's (binary search trees) that store values 1...n.For example,Given n = 3, your program should return all 5 unique BST's shown below. 1 3

2014-02-10 13:39:29 1738

原创 [leet code] Partition List Pow(x, n)

Implement pow(x, n).===========Analysis:The most basic idea, x multiply itself n time and return. However, this strait forward approach got time excessed. O(n).Note that O(logn)Accordingl

2014-02-10 00:55:07 653

原创 [leet code] Partition List

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.You should preserve the original relative order of the nodes in each of

2014-02-09 06:46:36 1962

原创 [leet code] Triangle

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], [

2014-02-08 10:25:40 950

原创 [leet code] Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be chosen from C unlimited numb

2014-02-08 06:40:00 787

原创 [leet code] Binary Tree Zigzag Level Order Traversal

Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).For example:Given binary

2014-02-08 00:57:21 1346

原创 [leet code] Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree should look like: 1

2014-02-08 00:13:35 979

原创 [leet code] Permutations II

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].

2014-02-07 01:30:01 792

原创 [leet code] Count and Say

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

2014-02-06 04:54:46 829

原创 [leet code] Longest Consecutive Sequence

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

2014-02-05 07:48:58 836

原创 [CrackCode] 5.5 Determine the number of bits required to convert integer A to integer B

Write a function to determine the number of bits required to convert integer A tointeger BInput: 31, 14Output: 2 =========Analysis:Basic idea of mine is to compare each digit

2014-02-05 06:23:14 693

原创 [CrackCode] 5.3 Print the next smallest and next largest number

Given an integer, print the next smallest and next largest number that have the same number of 1 bits in their binary representation ================Analysis:Assume that we are given 1

2014-02-05 05:57:16 911

原创 [CrackCode] 5.2 Print the binary representation

Given a (decimal - e g 3.72) number that is passed in as a string, print the binary rep-resentation If the number can not be represented accurately in binary, print “ERROR” ============A

2014-02-05 00:18:55 1810

原创 [CrackCode] 5.1 Set all bits between i and j in N equal to M

You are given two 32-bit numbers, N and M, and two bit positions, i and j Write amethod to set all bits between i and j in N equal to M (e g , M becomes a substring ofN located at i and starting at

2014-02-04 07:27:42 1029

原创 [leet code] Subsets II

Given a collection of integers that might contain duplicates, S, return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution set must not contain dupli

2014-02-04 02:57:33 686

原创 [CrackCode] 4.4 Creates a linked list of all the nodes at each depth of a given tree

Given a binary search tree, design an algorithm which creates a linked list of all thenodes at each depth (eg, if you have a tree with depth D, you’ll have D linked lists) ==============

2014-02-03 06:15:05 1518

原创 [leet code] Valid Sudoku

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 fille

2014-02-03 01:32:12 5770

原创 [leet code] Jump Game

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 i

2014-01-29 08:10:09 834

原创 [leet code] Unique Paths II

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

2014-01-29 01:15:44 1589

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