2023
02-21
02-21
使用线段树求区间和
线段树（Segment Tree）是一种二叉搜索树，与区间树相似，他将一个区间划分成一些单元区间，每个单元区间对应线段树中的一个叶子节点。使用线段树可以快速的查找某一个节点在若干条线段中出现的次数，时间复杂度为 O(logN)。而未优化的空间复杂度为 2N ，实际应用时一般还要开 4N 的数组以免.... Read More >
标签归档：LeetCode
线段树（Segment Tree）是一种二叉搜索树，与区间树相似，他将一个区间划分成一些单元区间，每个单元区间对应线段树中的一个叶子节点。使用线段树可以快速的查找某一个节点在若干条线段中出现的次数，时间复杂度为 O(logN)。而未优化的空间复杂度为 2N ，实际应用时一般还要开 4N 的数组以免.... Read More >
2023
02-21
02-21
树状数组 —— 一种支持单点修改和区间查找的数据结构
树状数组（英语：Binary Indexed Tree）又称为二元索引树，由 Fenwick 于 1994年发明，故又称为 Fenwick 树，其初衷是解决数据压缩里的累积频率（Cumulative Frequency）的计算问题，现多用于高效计算数列的前缀和、区间和。它支持在 O(logn) 的时.... Read More >
2020
03-16
03-16
[LeetCode每日一题]264. Ugly Number II
![[LeetCode每日一题]264. Ugly Number II](https://weiguangli.com/wp-content/themes/frontopen2_v1.5.04.15/timthumb.php?src=https://weiguangli.com/wp-content/uploads/2020/02/LeetCode_Sharing.png&h=140&w=205&zc=1)
题目如下：
Write a program to find the n-th ugly number.
Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.
Example:
Input: n.... Read More >
2020
03-16
03-16
[LeetCode每日一题]263. Ugly Number
题目如下：
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.... Read More >
2020
03-12
03-12
[LeetCode每日一题]213. House Robber II
题目如下：
You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this plac.... Read More >
2020
03-12
03-12
[LeetCode每日一题]198. House Robber
题目如下：
You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint sto.... Read More >
2020
03-11
03-11
[LeetCode每日一题]140. Word Break II
题目如下：
Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, add spaces in s to construct a sentence where each .... Read More >
2020
03-08
03-08
[LeetCode每日一题]139. Word Break
题目如下：
Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separa.... Read More >
题目如下：
Given an integer n, generate all structurally unique BST's (binary search trees) that store values 1 ... n.
Example:
Input: 3
Output:
[
[1.... Read More >
题目如下：
Given n, how many structurally unique BST's (binary search trees) that store values 1 ... n?
Example:
Input: 3
Output: 5
Explanation:
Given .... Read More >