walter1990-CSDN博客

原创 leetcode 199 Binary Tree Right Side View

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.For example:Given the following binary tree, 1

2016-07-08 23:18:20 550

原创 Boosting 和 Gradient Boosting 理解

Boosting主要是一种思想，表示“知错就改”。而Gradient Boosting是在这个思想下的一种函数(也可以说模型)的优化方法，首先将函数(模型)分解为可加的形式(其实所有的函数都是可加的，只是是否好放在这个框架中，以及最终的效果如何)。然后进行m次迭代，通过使得损失函数在梯度上减少，最终得到一个优秀的模型。值得一提的是，每次模型在梯度方向上减少的部分，可以认为是一个“小”或者"弱"的模

2016-07-05 11:02:28 9556

原创 leetcode 145 Binary Tree Postorder Traversal

Given a binary tree, return the postorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [3,2,1].Note: Recursive solut

2016-07-03 20:58:36 455 1

原创 leetcode 137 Single Number II

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 usi

2016-07-03 20:25:51 412

原创 leetcode 139 Word Break

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.For example, givens = "leetcode",dict = ["leet"

2016-07-03 14:15:09 337

原创 indeed contenst

#include #include using namespace std;char g[6][7];int row[6];int f[6][1<<6][1<<12];inline bool valid(int x) { int ret = 0; while(x) { x &= (x-1); ret += 1; } return ret == 3;}int

2016-07-03 13:35:31 334

原创 leetcode 84 Largest Rectangle in Histogram

Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.Above is a histogram where width o

2016-06-30 21:15:08 290

原创 leetcode 278 First Bad Version

You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the

2016-06-29 19:31:29 317

原创 leetcode 283 Move Zeroes

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.For example, given nums = [0, 1, 0, 3, 12], after calling you

2016-06-27 13:35:36 315

原创 leetcode 242 Valid Anagram

Given two strings s and t, write a function to determine if t is an anagram of s.For example,s = "anagram", t = "nagaram", return true.s = "rat", t = "car", return false.Note:You may ass

2016-06-27 12:27:49 249

原创 leetcode 344 Reverse String

Write a function that takes a string as input and returns the string reversed.Example:Given s = "hello", return "olleh".Subscribe to see which companies asked this questionclass So

2016-06-26 19:51:13 233

原创 leetcode 345 Reverse Vowels of a String

Write a function that takes a string as input and reverse only the vowels of a string.Example 1:Given s = "hello", return "holle".Example 2:Given s = "leetcode", return "leotcede".

2016-06-26 19:45:52 376

原创 leetcode 257 Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.For example, given the following binary tree: 1 / \2 3 \ 5All root-to-leaf paths are:["1->2->5", "1->3"]Cre

2016-06-26 19:30:55 254

原创 leetcode 263 Ugly Number

Write a program to check whether a given number is an ugly number.Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly sinc

2016-06-26 18:50:41 267

原创 leecode 223 Rectangle Area

Find the total area covered by two rectilinear rectangles in a 2D plane.Each rectangle is defined by its bottom left corner and top right corner as shown in the figure.Assume that the tota

2016-06-26 10:48:31 264

原创 leetcode 342 Power of Four

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.Example:Given num = 16, return true. Given num = 5, return false.Follow up: Could you solve it without

2016-06-26 10:02:24 294

原创 leetcode 160 Intersection of Two Linked Lists

Write a program to find the node at which the intersection of two singly linked lists begins.For example, the following two linked lists:A: a1 → a2 ↘

2016-06-26 09:34:44 285

原创 leetcode 165 Compare Version Numbers

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 co

2016-06-25 14:37:40 235

原创 leetcode 219 Contains Duplicate II

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and jis at most k.S

2016-06-25 10:52:10 288

原创 leetcode 217 Contains Duplicate

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is

2016-06-23 23:08:08 225

原创 leetcode 206 Reverse Linked List

Reverse a singly linked list.click to show more hints.Subscribe to see which companies asked this question/** * Definition for singly-linked list. * struct ListNode { * int va

2016-06-23 22:39:05 184

原创 leetcode 205 Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced with anot

2016-06-23 22:01:22 294

原创 leetcode 204 Count Primes

Description:Count the number of prime numbers less than a non-negative number, n.Credits:Special thanks to @mithmatt for adding this problem and creating all test cases.class Solutio

2016-06-23 15:44:13 211

原创 leetcode 221 Maximal Square

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing all 1's and return its area.For example, given the following matrix:1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0

2016-06-23 15:16:46 257

原创 leetcode 203 Remove-Linked-List-Elements

Remove all elements from a linked list of integers that have value val.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5Credits:Special thanks

2016-06-20 21:45:24 231

原创 leetcode 202 Happy Number

Write an algorithm to determine if a number is "happy".A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares

2016-06-20 21:33:01 220

原创 leetcode 198 House Robber

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 house

2016-06-20 20:44:43 235

原创 leetcode 191 Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).For example, the 32-bit integer ’11' has binary representation 000000

2016-06-19 15:15:11 191

原创 leetcode 190 Reverse Bits

Reverse bits of a given 32 bits unsigned integer.For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as00111001

2016-06-19 15:01:46 278

原创 leetcode 189 Rotate Array

Rotate an array of n elements to the right by k steps.For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].Note:Try to come up as many solutions as yo

2016-06-19 14:29:01 235

原创 leetcode 172 Factorial Trailing Zeroes

Given an integer n, return the number of trailing zeroes in n!.Note: Your solution should be in logarithmic time complexity.Credits:Special thanks to @ts for adding this problem and creating

2016-06-19 14:16:37 206

原创 leetcode 171 Excel Sheet Column Number

Related to question Excel Sheet Column TitleGiven a column title as appear in an Excel sheet, return its corresponding column number.For example: A -> 1 B -> 2 C -> 3 ...

2016-06-18 16:31:03 214

原创 leetcode 169 Majority Element

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.You may assume that the array is non-empty and the majority element

2016-06-18 16:17:31 268

原创 leetcode 168 Excel Sheet Column Title

Given a positive integer, return its corresponding column title as appear in an Excel sheet.For example: 1 -> A 2 -> B 3 -> C ... 26 -> Z 27 -> AA 28 -> AB Credits

2016-06-18 16:05:27 217

原创 leetcode 155 Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top() -- Get

2016-06-18 15:37:23 192

原创 leetcode 141 Linked List Cycle

Given a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?Subscribe to see which companies asked this question/** * Definition fo

2016-06-18 15:10:50 195

原创 leetcode 125 Valid Palindrome

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a

2016-06-18 14:55:42 199

原创 leetcode 121 Best Time to Buy and Sell Stock II

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, bu

2016-06-16 23:48:44 227

原创 leetcode 121 Best Time to Buy and Sell Stock

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),

2016-06-16 23:41:43 222

原创 leetcode 120 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], [

2016-06-12 23:50:45 230

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