| 1 |
Two Sum |
C++ |
|
| 2 |
Add Two Numbers |
JAVA |
|
| 3 |
Longest Substring Without Repeating Characters |
JAVA |
维护前后两个指针 |
| 5 |
Longest Palindromic Substring |
JAVA |
dp做O(n^2)，Manacher算法可以做到O(n) |
| 6 |
ZigZag Conversion |
JAVA |
|
| 7 |
Reverse Integer |
JAVA |
神TM样例还越界了，最后居然上了trycatch |
| 8 |
String to Integer (atoi) |
JAVA |
|
| 9 |
Palindrome Number |
JAVA |
|
| 10 |
Container With Most Water |
JAVA |
h[l]小于h[r]时左移l，舍弃了(l,r-1)(l,r-2)..这样的区间，这样的区间是比(l,r)的值小的 |
| 11 |
Integer to Roman |
JAVA |
|
| 12 |
Roman to Integer |
JAVA |
|
| 14 |
Longest Common Prefix |
JAVA |
|
| 15 |
3Sum |
JAVA |
快排nlgn，枚举一个数再维护前后两个指针遍历一共O(n^2)，再处理一些重复答案的细节 |
| 16 |
3Sum Closest |
JAVA |
和上道题思路相同 |
| 17 |
Letter Combinations of a Phone Number |
JAVA |
dfs |
| 18 |
4Sum |
JAVA |
和15思路相同O(n^3)，再预判断一些可能的最小值和最大值可以大幅减少时间 |
| 19 |
Remove Nth Node From End of List |
JAVA |
前后两个指针，后指针到底时删前指针的，头部单独处理 |
| 20 |
Valid Parentheses |
JAVA |
|
| 21 |
Merge Two Sorted Lists |
JAVA |
递归从尾部开始 |
| 22 |
Generate Parentheses |
JAVA |
顺手测了下sb还是比string快多了 |
| 24 |
Swap Nodes in Pairs |
JAVA |
|
| 26 |
Remove Duplicates from Sorted Array |
JAVA |
|
| 27 |
Remove Element |
JAVA |
|
| 28 |
Implement strStr() |
JAVA |
KMP |
| 29 |
Divide Two Integers |
JAVA |
O(logn)实现除法 |
| 31 |
Next Permutation |
JAVA |
根据全序列的定义模拟 |
| 34 |
Search for a Range |
JAVA |
左右二分查找 |
| 35 |
Search Insert Position |
JAVA |
|
| 36 |
Valid Sudoku |
JAVA |
用二维数组来标记TF |
| 38 |
Count and Say |
JAVA |
|
| 39 |
Combination Sum |
JAVA |
dfs |
| 40 |
Combination Sum II |
JAVA |
|
| 43 |
Multiply Strings |
JAVA |
大数相乘的逻辑，没处理好逻辑WA了好多发，Karatsuba可以做到O(n^1.58) |
| 46 |
Permutations |
JAVA |
dfs不好处理已经用过的数，用数字对换做比较方便 |
| 47 |
Permutations II |
JAVA |
没想通重复的原因，在46的基础上加了个答案判重，效率极低，哪天智商高点的时候再来想想 |
| 47 |
Permutations II |
JAVA |
不用对换了，上dfs了，重复数字必须从前往后搜索 |
| 48 |
Rotate Image |
JAVA |
|
| 49 |
Group Anagrams |
JAVA |
HashMap的使用、遍历；String、List的排序 |
| 50 |
Pow(x, n) |
[JAVA](./pow(x, n)/Pow.java) |
先写了理论上也是二分的超时了，原因改天再想，换了种思路二分递归 |
| 53 |
Maximum Subarray |
JAVA |
O(n)最大子数组 |
| 54 |
Spiral Matrix |
JAVA |
模拟 |
| 55 |
Jump Game |
JAVA |
|
| 58 |
Length of Last Word |
JAVA |
|
| 59 |
Spiral Matrix II |
JAVA |
|
| 60 |
Permutation Sequence |
JAVA |
神TM时间超过了99%的提交，写的有点难懂，大概就是取(n-i)!来判断第i位是什么 |
| 61 |
Rotate List |
JAVA |
|
| 62 |
Unique Paths |
JAVA |
dp |
| 63 |
Unique Paths II |
JAVA |
dp |
| 64 |
Minimum Path Sum |
JAVA |
dp三连 |
| 66 |
Plus One |
JAVA |
|
| 67 |
Add Binary |
JAVA |
|
| 69 |
Sqrt(x) |
JAVA |
|
| 70 |
Climbing Stairs |
JAVA |
dp |
| 71 |
Simplify Path |
JAVA |
|
| 73 |
Set Matrix Zeroes |
JAVA |
|
| 74 |
Search a 2D Matrix |
JAVA |
标准二分 |
| 75 |
Sort Colors |
JAVA |
|
| 77 |
Combinations |
JAVA |
|
| 78 |
Subsets |
JAVA |
|
| 79 |
Word Search |
JAVA |
|
| 80 |
Remove Duplicates from Sorted Array II |
JAVA |
|
| 33 |
Search in Rotated Sorted Array |
JAVA |
二分，逻辑有点乱，自己都不知道怎么过的 |
| 81 |
Search in Rotated Sorted Array II |
JAVA |
上一道题的加强版，逻辑理清了二分还是很简单的 |
| 82 |
Remove Duplicates from Sorted List II |
JAVA |
做了补头不补头两个版本，这种涉及头部变化的最好补头，不然逻辑很乱 |
| 83 |
Remove Duplicates from Sorted List |
JAVA |
上一道题的弱化版，最直观的就是头部不会变化了，这种就不用补头，而且特简单 |
| 86 |
Partition List |
JAVA |
现在想想只要不重新申请一个链表出来，申请个头部、几个指针什么的还是合理的，而且会让问题很简单，没有必要非要在原链表上进行直接操作 |
| 88 |
Merge Sorted Array |
JAVA |
从后往前避免覆盖 |
| 89 |
Gray Code |
JAVA |
|
| 90 |
Subsets II |
JAVA |
78上加一行 |
| 91 |
Decode Ways |
JAVA |
dp |
| 92 |
Reverse Linked List II |
JAVA |
三个指针翻转 |
| 93 |
Restore IP Addresses |
JAVA |
|
| 94 |
Binary Tree Inorder Traversal |
JAVA |
标准中序遍历 |
| 95 |
Unique Binary Search Trees II |
JAVA |
二叉搜索树的生成，递归有点绕，回头再做一遍（而且做的其实不严谨，这里面的下层节点都用的一个引用，这些生成的搜索树都没有分开） |
| 96 |
Unique Binary Search Trees |
JAVA |
95的逻辑，dp |
| 98 |
Validate Binary Search Tree |
JAVA |
BST的定义是左子树的所有节点都要比根节点小，右同，因此用min、max对子树进行界限规定，使用Integer可取null值表示不受限 |
| 98 |
Validate Binary Search Tree |
JAVA |
BST的中序遍历是递增数列，以此判断，效率不如上面的做法 |
| 100 |
Same Tree |
JAVA |
|
| 101 |
Symmetric Tree |
JAVA |
100改一行 |
| 102 |
Binary Tree Level Order Traversal |
JAVA |
bfs |
| 103 |
Binary Tree Zigzag Level Order Traversal |
JAVA |
bfs，往头部添加元素用LinkedList |
| 104 |
Maximum Depth of Binary Tree |
JAVA |
bfs |
| 104 |
Maximum Depth of Binary Tree |
JAVA |
dfs |
| 105 |
Construct Binary Tree from Preorder and Inorder Traversal |
JAVA |
前序中序构造树 |
| 105 |
Construct Binary Tree from Preorder and Inorder Traversal |
JAVA |
这道题测试用例的原因，导致把从前往后查找改成从后往前查找就超过了99%的提交，我还以为那些快的是什么新方法呢 |
| 106 |
Construct Binary Tree from Inorder and Postorder Traversal |
JAVA |
中序后序构造树 |
| 107 |
Binary Tree Level Order Traversal II |
JAVA |
|
| 108 |
Convert Sorted Array to Binary Search Tree |
JAVA |
|
| 109 |
Convert Sorted List to Binary Search Tree |
JAVA |
快慢指针+二分O(nlogn)超时了，转数组后108解O(n)即可 |
| 56 |
Merge Intervals |
JAVA |
|
| 110 |
Balanced Binary Tree |
JAVA |
|
| 111 |
Minimum Depth of Binary Tree |
JAVA |
|
| 112 |
Path Sum |
JAVA |
|
| 113 |
Path Sum II |
JAVA |
|
| 114 |
Flatten Binary Tree to Linked List |
JAVA |
|
| 116 |
Populating Next Right Pointers in Each Node |
JAVA |
bfs |
| 116 |
Populating Next Right Pointers in Each Node |
JAVA |
dfs递归 |
| 117 |
Populating Next Right Pointers in Each Node II |
JAVA |
116 bfs 一模一样 |