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Commit bc6f1a9

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新增排序和二分部分题目
1 parent d52018d commit bc6f1a9

27 files changed

+856
-148
lines changed

‎README.md‎

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Original file line numberDiff line numberDiff line change
@@ -30,16 +30,24 @@
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| 34 | [在排序数组中查找元素的第一个和最后一个位置](https://leetcode-cn.com/problems/find-first-and-last-position-of-element-in-sorted-array/)| [searchRange](./bsearch/leetcode/medium/searchRange.h) | <font color=orange> medium </font> | ✅|
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| 35 | [搜索插入位置](https://leetcode-cn.com/problems/search-insert-position/) | [searchInsert](./array/leetcode/easy/searchInsert.h) | <font color=green>easy</font> | ✅ |
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| 36 | [有效的数独](https://leetcode-cn.com/problems/valid-sudoku/)| [isValidSudoku](./other/leetcode/medium/isValidSudoku.h) | <font color=orange> medium </font> | ✅|
33-
| 39 | [组合总和](https://leetcode-cn.com/problems/combination-sum/)| [combinationSum](./array/leetcode/medium/combinationSum.h) | <font color=orange> medium </font> | ✅|
33+
| 39 | [组合总和](https://leetcode-cn.com/problems/combination-sum/)| [combinationSum](./backtracking/leetcode/medium/combinationSum.h) | <font color=orange> medium </font> | ✅|
34+
| 46 | [全排列](https://leetcode-cn.com/problems/permutations/)| [permutations](./backtracking/leetcode/medium/permutations.h) | <font color=orange> medium </font> | ✅|
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| 53 | [最大子序和](https://leetcode-cn.com/problems/maximum-subarray/) | [maxSubArray](./array/leetcode/easy/maxSubArray.h) | <font color=green>easy</font> | ✅ |
36+
| 56 | [合并区间](https://leetcode-cn.com/problems/merge-intervals/) | [merge_intervals](./sort/leetcode/merge_intervals.h) | <font color=orange> medium </font> | ✅ |
3537
| 58| [最后一个单词的长度](https://leetcode-cn.com/problems/length-of-last-word) | [lengthOfLastWord](./string/leetcode/easy/lengthOfLastWord.h) | <font color=green>easy</font> | ✅ |
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| 66 | [加一](https://leetcode-cn.com/problems/plus-one/) | [plusOne](./array/leetcode/easy/plusOne.h) | <font color=green>easy</font> | ✅ |
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| 67 | [二进制求和](https://leetcode-cn.com/problems/add-binary/) | [addBinary](./array/leetcode/easy/addBinary.h) | <font color=green>easy</font> | ✅ |
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| 69 | [x 的平方根](https://leetcode-cn.com/problems/sqrtx/%E2%80%A8)| [mySqrt](./bsearch/leetcode/mySqrt.h) | <font color=green>easy</font> | ✅ |
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| 70 | [爬楼梯](https://leetcode-cn.com/problems/climbing-stairs/)| [climbStairs](./dp/leetcode/easy/climbStairs.h) | <font color=green>easy</font> | ✅ |
42+
| 75 | [颜色分类](https://leetcode-cn.com/problems/sort-colors/) | [sort_colors](./sort/leetcode/sort_colors.h) | <font color=orange> medium </font> | ✅ |
4043
| 83 | [删除排序链表中的重复元素](https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list/)| [deleteDuplicates](./linkedList/leetcode/easy/deleteDuplicates.h) | <font color=green>easy</font> | ✅ |
4144
| 88 | [合并两个有序数组](https://leetcode-cn.com/problems/merge-sorted-array/) | [merge](./array/leetcode/easy/merge.h) | <font color=green>easy</font> | ✅ |
4245
| 100 | [相同的树](https://leetcode-cn.com/problems/same-tree/) | [isSameTree](./tree/leetcode/easy/isSameTree.h) | <font color=green>easy</font> | ✅ |
46+
| 687 | [最长同值路径](https://leetcode-cn.com/problems/longest-univalue-path/)| [longestUnivaluePath](./recursion/leetcode/medium/longestUnivaluePath.h) | <font color=green>easy</font> | ✅ |
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----------------
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-----------------
@@ -55,6 +63,39 @@
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## [递归](./recursion.md) 🚶🚶🚶🚶
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### 什么是递归?
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试想一下电影院自己在第几排的场景, 想要知道我在第几排,那么就要去问前面的人他处于第几排,那么前面的人又怎么知道他自己在第几排呢?那自然是他也要去问他前面的人咯.
70+
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这就是递归的场景,去的过程叫做<font size=5 color=red>"递"</font>, 回来的过程叫做<font size=5 color=red>"归"</font>,有来有回。
72+
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![](./res/recursion_example.png)
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<font size=5 color=red>递归其实就是利用栈的数据结构,再加上一些简单的逻辑算法从而完成了问题的求解。只不过这个栈是由系统来提供的,我们只是无感知罢了.</font>
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### 适合场景
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满足下面两点:
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* 一个问题的解可以分解为几个子问题(规模更小的问题)的解, 并且子问题和问题除了数据规模不一样,求解思路是完全一样的。
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* 存在终止条件
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那么如何编写递归代码呢?
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关键在于找到将大问题分解为小问题的规律,写出递归公式,然后在推敲出终止条件。
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递归代码简洁高效,但是容易出现堆栈溢出,重复计算,函数调用耗时多,空间复杂度高等问题。一般嵌套比较少的场景可以使用递归。
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### [递归题目](./recursion.md)
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## [排序](./sort.md)
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## [二分查找](./bsearch.md)
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* 二分查找
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## [链表](./linkedlist.md)
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## [链表](./linkedList.md)
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## [栈&队列](./stack_queue.md)
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## [树](./tree.md)

‎alg-cpp.xcodeproj/project.pbxproj‎

Lines changed: 28 additions & 2 deletions
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225-
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226231
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091A5E17231EC2AE000BEFAF /* sort_colors.h */,
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09CA9FAE2318A7A500BE2B39 /* permutations.h */,
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091A5E13231EB6E4000BEFAF /* leetcode */,
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@@ -827,6 +849,10 @@
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829851
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sourceTree = "<group>";
13.5 KB
Binary file not shown.

‎backtracking.md‎

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| &emsp;题号&emsp; | 题目链接&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;| 答案链接&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;| &emsp;难度&emsp; | &emsp;完成度&emsp; |
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| :--: | :--: | :----------------------------------------------------------- | :----------------------------------------------------------- | :------: |
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| 17 | [电话号码的字母组合](https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number/) | [letter_combinations_of_a_phone_number](./backtracking/leetcode/medium/letter_combinations_of_a_phone_number.h) | <font color=orange> medium </font> | ✅ |
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| 39 | [组合总和](https://leetcode-cn.com/problems/combination-sum/)| [combinationSum](./backtracking/leetcode/medium/combinationSum.h) | <font color=orange> medium </font> | ✅|
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| 46 | [全排列](https://leetcode-cn.com/problems/permutations/)| [permutations](./backtracking/leetcode/medium/permutations.h) | <font color=orange> medium </font> | ✅|
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### 剑指Offer
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//
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// permutations.h
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// recursion
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//
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// Created by junlongj on 2019年8月30日.
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// Copyright © 2019 junl. All rights reserved.
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//
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#ifndef permutations_hpp
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#define permutations_hpp
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#include <stdio.h>
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#include <vector>
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/*
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46.全排列
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给定一个没有重复数字的序列,返回其所有可能的全排列。
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示例:
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输入: [1,2,3]
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输出:
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[
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[1,2,3],
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[1,3,2],
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[2,1,3],
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[2,3,1],
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[3,1,2],
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[3,2,1]
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]
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来源:力扣(LeetCode)
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链接:https://leetcode-cn.com/problems/permutations
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著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
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*/
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namespace leetcode {
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using namespace std;
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class Solution_46 {
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public:
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vector<vector<int>> permute(vector<int>& nums) {
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vector<int> elements;
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permute(nums, elements);
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return results;
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}
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private:
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vector<vector<int>> results;
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void permute(vector<int>& nums, vector<int> elements) {
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//终止条件
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if (elements.size() == nums.size()){
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results.push_back(elements);
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return;
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}
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//递归公式
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for (auto &num : nums){
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if(find(elements.begin(),elements.end(),num) != elements.end())
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continue;
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elements.push_back(num);
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permute(nums, elements);
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elements.pop_back();
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}
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}
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};
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}
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#endif /* permutations_hpp */

‎bsearch.md‎

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## 二分查找
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### leetcode
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# 二分查找
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二分查找是在<font size=5 color=red>有序集合中快速寻找某个元素</font>的算法, 它的时间复杂度为O(logn)是一种非常高效的查找算法。<font size=5 color=red>二分查找每次都通过和区间的中间元素作对比,来将查找区间缩小为之前的一半,直到找到元素或区间缩小为一.</font>
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二分适合的场景:
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1. 二分查找依赖于数组结构的随机访问能力,对于其他数据结构无法适用。
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2. 数组里面的元素必须是有序的,即如果我们是一次排序N次二分查找,那么可以平摊掉排序的时间,如果数据集合是频繁插入,删除,那么每次二分之前就需要先排序,在查找了,二分就不适合了.
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3. 数据量太小不适合用二分查找,比如10次以内的循环,其实直接顺序遍历时间也差不多。但是如果涉及到元素比较比较耗时(比如长字符串直接的比较),那么比较次数越少越好
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4. 数据量太大也不适用于二分查找。因为二分需要依靠数组,而数组是无法存储大数据的。
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## [二分查找基本代码](./bsearch/bsearch.h)
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二分查找变形问题
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## [查找第一个值等于给定值的元素](./bsearch/bsearch_findFirstElement.h)
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## [查找最后一个值等于给定值的元素](./bsearch/bsearch_findLastElement.h)
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## [ 查找第一个大于等于指定元素的值](./bsearch/bsearch_findFirstElementGreaterOrEqual.h)
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## [查找最后一个小于等于给定值的元素](./bsearch/bsearch_findLastElementLessOrEqual.h)
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在排序数组中寻找一个指定的数,我们既可以使用二分,也可以使用二叉树,散列表等数据结构。虽然后者会使用更多内存,但是当内存不是如此紧缺的情况下,使用后者也能做到。那么二分的优势何在呢?
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<font size=5 color=red>二分法更适合用于"近似查找"问题</font>,比如刚刚的几个变种问题,如果使用散列表等结构就做不到了。
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## leetcode
335
| &emsp;题号&emsp; | 题目链接&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;| 答案链接&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;| &emsp;难度&emsp; | &emsp;完成度&emsp; |
436
| :--: | :--: | :----------------------------------------------------------- | :----------------------------------------------------------- | :------: |
537
| 33 | [搜索旋转排序数组](https://leetcode-cn.com/problems/search-in-rotated-sorted-array)| [searchInRotatedSortedArray](./bsearch/leetcode/medium/searchInRotatedSortedArray.h) | ✨✨ | ✅|

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