leetCode刷题顺序 - HelloWorld开发者社区

leetCode题太多了，自己还是一个非计算机专业的小白，所有问题都刷他困难了，所以挑选典型的进行刷，然后自己总结。以下为需要刷的类型和题目，没有行号，我每刷过一个道在加行号；每一个模块完后会总结思路；
刷的题目是参考其他博主的，但是学到东西是自己的。

1. Pattern: Sliding window，滑动窗口类型

Maximum Sum Subarray of Size K (easy)
Smallest Subarray with a given sum (easy)
Longest Substring with K Distinct Characters (medium)
Fruits into Baskets (medium)
No-repeat Substring (hard)
Longest Substring with Same Letters after Replacement (hard)
Longest Subarray with Ones after Replacement (hard)

2.Pattern: two points, 双指针类型

Pair with Target Sum (easy)
Remove Duplicates (easy)
Squaring a Sorted Array (easy)
Triplet Sum to Zero (medium)
Triplet Sum Close to Target (medium)
Triplets with Smaller Sum (medium)
Subarrays with Product Less than a Target (medium)
Dutch National Flag Problem (medium)

3.Pattern: Fast & Slow pointers, 快慢指针类型

LinkedList Cycle (easy)
Start of LinkedList Cycle (medium)
Happy Number (medium)
Middle of the LinkedList (easy)

4.Pattern: Merge Intervals，区间合并类型

Merge Intervals (medium)
Insert Interval (medium)
Intervals Intersection (medium)
Conflicting Appointments (medium)

5. Pattern: Cyclic Sort，循环排序

Cyclic Sort (easy)
Find the Missing Number (easy)
Find all Missing Numbers (easy)
Find the Duplicate Number (easy)
Find all Duplicate Numbers (easy)

6.Pattern: In-place Reversal of a LinkedList，链表翻转

Reverse a LinkedList (easy)
Reverse a Sub-list (medium)
Reverse every K-element Sub-list (medium)

7.Pattern: Tree Breadth First Search，树上的BFS

Binary Tree Level Order Traversal (easy)[102]
Binary Tree Zigzag Level Order Traversal (medium)[103]

在102基础上使用双端队列就可以解决；add,push；每次拿都是从队尾；

Level Averages in a Binary Tree (easy)[637] 同样的bfs层序遍历，只需要注意dubble这个类型；
Minimum Depth of a Binary Tree (easy)[111] 这个用深度优先很好算但是广度优先也是可以的；将node和封装到同一个node里边；如果当前节点左右都为空，这个深度就是你想要的的；输的高度就是树的层数；bfs会优先找到深度最浅的的叶子节点；

使用bfs有一个通用的模板就是用一个队列或者双端队列去存储一层的树节点，然后一直遍历；这个规律是死的

Queue/ Dueue  queue = new LinkedList<>();
queue.offer(root);
while(!queue.isEmpty()){
    int len = queue.size();// 一定要提前记录否则你poll时候会减少；
    for(int i=0;i<len;i++）{
        TreeNode node = queue.poll();
        if(node.left!=null){
            queue.offer(node.left);
        }
        if(node.right!=null){
            queue.offer(node.right());
        }
    }
}

8.Pattern: Tree Depth First Search，树上的DFS

Binary Tree Path Sum (easy)[112]
Path Sum II (medium)[113]
Same Tree[100]
Symmetric Tree[101] 分成两个root 进行比较左右；
Maximum Depth of Binary Tree[104] 左右深度对比；最深的是结果，Math.max();
Balanced Binary Tree[110]

首先你要知道什么平衡二叉树，null或者左右深度差不超过1 Math.abs;

对于DFS就是通过递归进行调用，递归没有固定的模板，但是有固定的思路；在递归中可以看看成数学的数学归纳法，我们先找到特例，也就是数学归纳法中的n=1的部分，对应理解就是你的临界条件。然后推理后边的，假设n-1成立去推，对应的理解就是n-1就是我们递归的那个方法；剩下的就得实战中自己悟，每个人都会有自己的一个理解；

public void dfs(){
    doSomething();
    dfs();//递归调用
}
public xx dfs(){   
    xx xx = dfs();//把这个看成数学归纳法中的n-1
     if 跳出条件；
    对xx操作；返回的就是这个xx
}

9. Pattern: Two Heaps，双堆类型

Find the Median of a Number Stream (medium)
Sliding Window Median (hard)
Maximize Capital (hard)

10. Pattern: Subsets，子集类型，一般都是使用多重DFS

Subsets (easy)
Subsets With Duplicates (easy)
Permutations (medium)
String Permutations by changing case (medium)
Balanced Parentheses (hard)
Unique Generalized Abbreviations (hard)

11. Pattern: Modified Binary Search，改造过的二分

Order-agnostic Binary Search (easy)
Ceiling of a Number (medium)
Next Letter (medium)
Number Range (medium)
Search in a Sorted Infinite Array (medium)
Minimum Difference Element (medium)
Bitonic Array Maximum (easy)

12. Pattern: Top ‘K’ Elements，前K个系列

Top ‘K’ Numbers (easy)
Kth Smallest Number (easy)
‘K’ Closest Points to the Origin (easy)
Connect Ropes (easy)
Top ‘K’ Frequent Numbers (medium)
Frequency Sort (medium)
Kth Largest Number in a Stream (medium)
‘K’ Closest Numbers (medium)
Maximum Distinct Elements (medium)
Sum of Elements (medium)
Rearrange String (hard)

13. Pattern: K-way merge，多路归并

Merge K Sorted Lists (medium)
Kth Smallest Number in M Sorted Lists (Medium)
Kth Smallest Number in a Sorted Matrix (Hard)
Smallest Number Range (Hard)

14. Pattern: 0/1 Knapsack (Dynamic Programming)，0/1背包类型

0/1 Knapsack (medium)
Equal Subset Sum Partition (medium)
Subset Sum (medium)
Minimum Subset Sum Difference (hard)

15. Pattern: Topological Sort (Graph)，拓扑排序类型

Topological Sort (medium)
Tasks Scheduling (medium)
Tasks Scheduling Order (medium)
All Tasks Scheduling Orders (hard)
Alien Dictionary (hard)

动态规划专题BP

0/1 Knapsack, 0/1背包，6个题

0/1 Knapsack，0/1背包问题

Equal Subset Sum Partition，相等子集划分问题

Subset Sum，子集和问题

Minimum Subset Sum Difference，子集和的最小差问题

Count of Subset Sum，相等子集和的个数问题

Target Sum，寻找目标和的问题

Unbounded Knapsack，无限背包，5个题

Unbounded Knapsack，无限背包

Rod Cutting，切钢条问题

Coin Change，换硬币问题

Minimum Coin Change，凑齐每个数需要的最少硬币问题

Maximum Ribbon Cut，丝带的最大值切法

Fibonacci Numbers，斐波那契数列，6个题

Fibonacci numbers，斐波那契数列问题

Staircase，爬楼梯问题

Number factors，分解因子问题

Minimum jumps to reach the end，蛙跳最小步数问题

Minimum jumps with fee，蛙跳带有代价的问题

House thief，偷房子问题

Palindromic Subsequence，回文子系列，5个题

Longest Palindromic Subsequence，最长回文子序列

Longest Palindromic Substring，最长回文子字符串

Count of Palindromic Substrings，最长子字符串的个数问题

Minimum Deletions in a String to make it a Palindrome，怎么删掉最少字符构成回文

Palindromic Partitioning，怎么分配字符，形成回文

Longest Common Substring，最长子字符串系列，13个题

Longest Common Substring，最长相同子串

Longest Common Subsequence，最长相同子序列

Minimum Deletions & Insertions to Transform a String into another，字符串变换

Longest Increasing Subsequence，最长上升子序列

Maximum Sum Increasing Subsequence，最长上升子序列和

Shortest Common Super-sequence，最短超级子序列

Minimum Deletions to Make a Sequence Sorted，最少删除变换出子序列

Longest Repeating Subsequence，最长重复子序列

Subsequence Pattern Matching，子序列匹配

Longest Bitonic Subsequence，最长字节子序列

Longest Alternating Subsequence，最长交差变换子序列

Edit Distance，编辑距离

Strings Interleaving，交织字符串