jianchao_li
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jianchao_li
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个人介绍
热爱人工智能、机器学习和算法；截至2018年1月2日，LeetCode用户Most Reputation排名第2（https://discuss.leetcode.com/users?section=sort-reputation）
擅长的技术
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发表了文章 2015-08-03
[LeetCode] Best Time to Buy and Sell Stock III
Personally, this is a relatively difficult DP problem. This link posts a typical DP solution to it. You may need some time to get how it works.
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发表了文章 2015-08-01
[LeetCode] Group Anagrams
The function signature has been updated to return a more intuitive vectorwhich treats a single string as a group of anagrams consisting of only itself.
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发表了文章 2015-08-01
[LeetCode] Valid Anagram
Hash Table This idea uses a hash table to record the times of appearances of each letter in the two stringss and t.
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发表了文章 2015-08-01
[LeetCode] Scramble String
To solve this problem, you first need to understand it well. The key problem is tell the difference of scramble from permutations.
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发表了文章 2015-07-27
[LeetCode] Different Ways to Add Parentheses
Well, this problem seems to be a little tricky at first glance. However, the idea (taken from this link) is really simple.
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发表了文章 2015-07-27
[LeetCode] Candy
Well, you may need to run some examples to have the intuition for the answer since we only require children with higher rating get more candies than their neighbors, not all those with lower ratings.
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发表了文章 2015-07-26
[LeetCode] Distinct Subsequences
Well, a dynamic programming problem. Let's first define its state dp[i][j] to be the number of distinct subsequences of t[0.
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发表了文章 2015-07-25
[LeetCode] Search a 2D Matrix II
Well, the idea is to search from the top-right element and then reduce the range for further searching by comparisons between target and the current element.
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发表了文章 2015-07-19
[LeetCode] Find Minimum in Rotated Sorted Array II
This problem is more or less the same as Find Minimum in Rotated Sorted Array. And one key difference is as stated in the solution tag.
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发表了文章 2015-07-19
[LeetCode] Find Minimum in Rotated Sorted Array
As explained in the Solution tag, the key to solving this problem is to use invariants. We set two pointers: l for the left and r for the right.
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发表了文章 2015-07-19
[LeetCode] Search in Rotated Sorted Array II
For those who have already solved Search in Rotated Sorted Array, this problem can be solved similarly using codes for that problem and simply adding codes to skip the duplicates.
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发表了文章 2015-07-18
[LeetCode] Search in Rotated Sorted Array
This problem is a nice application of binary search. The key lies in how to determine the correct half for target.
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发表了文章 2015-07-17
[LeetCode] Rotate List
Well, in the case of a linked list instead of an array, the problem becomes easier. We just need to find the node that will be the new head of the lis...
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发表了文章 2015-07-17
[LeetCode] Rotate Array
This problem, as stated in the problem statement, has a lot of solutions. Since the problem requires us to solve it in O(1) space complexity, I only show some of them in the following.
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发表了文章 2015-07-16
[LeetCode] Product of Array Except Self
The first answer in this link has a nice illustrative explanation. Suppose the given array is like [nums[0], nums[1], nums[2], nums[3]].
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发表了文章 2015-07-15
[LeetCode] Recover Binary Search Tree
As the note in the problem statement, this problem has a straight-forward O(n)-space solution, which is to generate the inorder traversal results of t...
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发表了文章 2015-07-15
[LeetCode] Jump Game II
This problem has a nice BFS structure. Let's illustrate it using the example nums = [2, 3, 1, 1, 4] in the problem statement.
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发表了文章 2015-07-15
[LeetCode] Jump Game
This problem has a very concise solution in this link, just 4-lines. The code is rewritten below. 1 class Solution { 2 public: 3 bool canJump(vector& nums) { 4 int i = 0, n = nums.
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发表了文章 2015-07-15
[LeetCode] Delete Node in a Linked List
Well, this problem is just a trick. In fact, we cannot really delete the given node, but just delete its next node after copying the data of the next node to it.
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发表了文章 2015-07-15
[LeetCode] Climbing Stairs
Note: If you feel unwilling to read the long codes, just take the idea with you. The codes are unnecessarily long due to the inconvenient handle of matrices.
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发表了文章 2015-07-14
[LeetCode] Trapping Rain Water
Note: The following idea is in fact from the last answer in this link, which leads to a clean code. I just reorganize it and add some explanations.
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发表了文章 2015-07-14
[LeetCode] Container With Most Water
Well, an interesting problem. If you draw some examples on a white board and try to figure out the regularities, you may have noticed that the key to ...
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发表了文章 2015-07-14
[LeetCode] Copy List with Random Pointer
Well, since we need to make a deep copy of the list and nodes in the list have a random pointer that may point to any node in the list (or NULL), we n...
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发表了文章 2015-07-14
[LeetCode] Longest Substring with At Most Two Distinct Characters
Problem Description Given a string, find the length of the longest substring T that contains at most 2 distinct characters.
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发表了文章 2015-07-14
[LeetCode] Text Justification
The key to this problem is to identify all the words that can be added to a line and then identify the places that require an additional space (to mak...
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发表了文章 2015-07-13
[LeetCode] The Skyline Problem
An interesting problem! But not very easy at first glance. You need to think very clear about how will a keypoint be generated.
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发表了文章 2015-07-13
[LeetCode] Lowest Common Ancestor of a Binary Tree
Well, a follow-up for the problem Lowest Common Ancestor of a Binary Search Tree. However, this time you cannot figure out which subtree the given nodes lie in according to their values.
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发表了文章 2015-07-12
[LeetCode] Longest Common Prefix
Use the strs[0] as the reference string and then compare it with the remaining strings from left to right.
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发表了文章 2015-07-11
[LeetCode] Path Sum II
Well, a typical backtracking problem. The code is as follows. You may walk through it using the example in the problem statement to see how it works.
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发表了文章 2015-07-11
[LeetCode] Path Sum
This problem has a very easy recursive code as follows. 1 class Solution { 2 public: 3 bool hasPathSum(TreeNode* root, int sum) { 4 ...
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发表了文章 2015-07-11
[LintCode] 寻找缺失的数
1 class Solution { 2 public: 3 /** 4 * @param nums: a vector of integers 5 * @return: an integer 6 */ 7 int ...
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发表了文章 2015-07-11
[LintCode] 最多有多少个点在一条直线上
1 /** 2 * Definition for a point. 3 * struct Point { 4 * int x; 5 * int y; 6 * Point() : x(0), y(0) {} 7 * Point(...
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发表了文章 2015-07-11
[LeetCode] Max Points on a Line
This problem has a naive idea, which is to traverse all possible pairs of two points and see how many other points fall in the line determined by them.
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发表了文章 2015-07-11
[LeetCode] Binary Tree Right Side View
A simple application of level-order traversal. Just push the last node in each level into the result.
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发表了文章 2015-07-11
[LeetCode] Populating Next Right Pointers in Each Node II
The problem becomes more difficult once the binary tree is not perfect. The idea is still similar to use a level-order traversal.
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发表了文章 2015-07-11
[LeetCode] Populating Next Right Pointers in Each Node
The idea is similar to a level-order traversal and remember to take full advantages of the prefect binary tree assumption in the problem statement.
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发表了文章 2015-07-11
[LeetCode] Valid Number
I guess some of you may have noticed that this seemingly simple problem has the lowest acceptance rate among all problems on the LeetCode OJ.
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发表了文章 2015-07-11
[LeetCode] Lowest Common Ancestor of a Binary Search Tree
Well, remember to take advantage of the property of binary search trees, which is, node -> left -> val < node -> val < node -> right -> val.
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发表了文章 2015-07-10
[LeetCode] Valid Palindrome
The suggested solution to this problem has given a clear idea. The tricky part of this problem is to handle all the edge cases carefully and write a clean code.
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发表了文章 2015-07-10
[LeetCode] Palindrome Linked List
The idea is not so obvious at first glance. Since you cannot move from a node back to its previous node in a singly linked list, we choose to reverse ...
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发表了文章 2015-07-08
[LeetCode] Binary Search Tree Iterator
The key to this problem is to store the values in a stack. In the constructor and next, we add all the next smallest nodes into the stack.
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发表了文章 2015-07-08
[LeetCode] Number of Digit One
The following idea is taken from a book named 《剑指offer》 published in China. Suppose n = 271, it then breaks [1, 271] into [1, 71] and [72, 271].
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发表了文章 2015-07-07
[LeetCode] Remove Nth Node From End of List
This is a classic problem of linked list. You may solve it using two pointers. The tricky part lies in the head pointer may also be the one that is required to be removed.
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发表了文章 2015-07-07
[LintCode] 删除链表中倒数第n个节点
1 /** 2 * Definition of ListNode 3 * class ListNode { 4 * public: 5 * int val; 6 * ListNode *next; 7 * ListNode(int v...
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发表了文章 2015-07-07
[LintCode] 在O(1)时间复杂度删除链表节点
1 /** 2 * Definition of ListNode 3 * class ListNode { 4 * public: 5 * int val; 6 * ListNode *next; 7 * ListNode(int v...
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发表了文章 2015-07-07
[LintCode] 丢失的第一个正整数
1 class Solution { 2 public: 3 /** 4 * @param A: a vector of integers 5 * @return: an integer 6 */ 7 int fir...
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发表了文章 2015-07-07
[LeetCode] First Missing Positive
This link has a nice explanation of the problem. I rewrite the code below. Play with it using some special examples and you will find out how it works.
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发表了文章 2015-07-07
[LeetCode] Implement Queue using Stacks
A classic interview question. This link has a nice explanation of the idea using two stacks and its amortized time complexity.
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发表了文章 2015-07-07
[LintCode] 带重复元素的排列
递归实现： 1 class Solution { 2 public: 3 /** 4 * @param nums: A list of integers. 5 * @return: A list of unique permutations.
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发表了文章 2015-07-07
[LintCode] 全排列
递归实现： class Solution { public: /** * @param nums: A list of integers. * @return: A list of permutations.
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发表了文章
2018-01-02
Jianchao's Blog is gonna to be moved to Yunqi
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发表了文章
2016-09-10
[LeetCode] Sum of Two Integers
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发表了文章
2016-08-14
[LeetCode] Ransom Note
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发表了文章
2015-12-03
[LeetCode] Sparse Matrix Multiplication
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发表了文章
2015-11-23
[LeetCode] Range Sum Query - Mutable
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发表了文章
2015-11-20
[LeetCode] Additive Number
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发表了文章
2015-11-14
[LeetCode] Number of Islands II
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发表了文章
2015-11-12
[LeetCode] Range Sum Query 2D - Immutable
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发表了文章
2015-11-10
[LeetCode] Range Sum Query - Immutable
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发表了文章
2015-11-08
[LeetCode] Smallest Rectangle Enclosing Black Pixels
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发表了文章
2015-11-05
[LeetCode] Remove Invalid Parentheses
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发表了文章
2015-11-03
[LeetCode] Longest Increasing Subsequence
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发表了文章
2015-10-31
[LeetCode] Bulls and Cows
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发表了文章
2015-10-30
[LeetCode] Binary Tree Longest Consecutive Sequence
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发表了文章
2015-10-30
[LeetCode] Serialize and Deserialize Binary Tree
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发表了文章
2015-10-22
[LeetCode] Best Meeting Point
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发表了文章
2015-10-19
[LeetCode] Find Median from Data Stream
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发表了文章
2015-10-17
[LeetCode] Flip Game II
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发表了文章
2015-10-15
[LeetCode] Flip Game
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发表了文章
2015-10-13
[LeetCode] Nim Game
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