Vampirelzl的博客

Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1’s in their binary representation and return them as an array.Example: For num = 5 you sh

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this p

Given a binary tree, find the leftmost value in the last row of the tree.Example 1:Input: 2 / \ 1 3Output:1Example 2: Input: 1 / \ 2 3 / / \ 4 5 6

Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element that appears only once.Example 1:Input: [1,1,2,3,3

Suppose you have N integers from 1 to N. We define a beautiful arrangement as an array that is constructed by these N numbers successfully if one of the following is true for the ith position (1 <= i <

Given a non-empty 2D array grid of 0’s and 1’s, an island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surroun

Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.算法解析：既可以用深度优先搜索，也可以用广度优先搜索，前者可以节省代码，后者可以提高速

Given a string, your task is to count how many palindromic substrings in this string.The substrings with different start indexes or end indexes are counted as different substrings even they consist of

You need to find the largest value in each row of a binary tree.Example:Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9]算法分析：考查BFS，或者说是树的层序遍历，但要注意区分每一层。我

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 me

Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.Find all the elements that appear twice in this array.Could you do it without extra space

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely s

Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.Note: 1. The given integer is guaranteed to fit within the range of a 3

The Hamming distance between two integers is the number of positions at which the corresponding bits are different.Given two integers x and y, calculate the Hamming distance.Note: 0≤x,y<2310 ≤ x, y <

Given an integer array with no duplicates. A maximum tree building on this array is defined as follow:The root is the maximum number in the array.The left subtree is the maximum tree constructed from

Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot makes a circle, which means it moves back to the original place.The move sequence is represented by a

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not.You need to merge them into a new binary tree. T

Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), …, (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possibl

Given a List of words, return the words that can be typed using letters of alphabet on only one row’s of American keyboard like the image below.Example 1:Input: ["Hello", "Alaska", "Dad", "Peace"]Outp

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.Example 1:Input: "Let's take LeetCode contest"Output

In MATLAB, there is a very useful function called ‘reshape’, which can reshape a matrix into a new one with different size but keep its original data.You’re given a matrix represented by a two-dimensio

Invert a binary tree. 4 / \ 2 7 / \ / \1 3 6 9to 4 / \ 7 2 / \ / \9 6 3 1算法分析：可以用层序遍历的方法交换左右子树，也可以直接递归。C语言版struct TreeNode* invertTree(struct TreeNode* roo