Ryan’s leetcode Blog

As the title described, you should only use two stacks to implement a queue's actions. The queue should support  push(element) ,  pop...

Given an directed graph, a topological order of the graph nodes is defined as follow: For each directed edge A-->B in graph, A must ...

Given an integer array, adjust each integers so that the difference of every adjcent integers are not greater than a given number target. ...

Given n distinct positive integers, integer k (k <= n) and a number target. Find k numbers where sum is target. Calculate how many sol...

Given n items with size A[i], an integer m denotes the size of a backpack. How full you can fill this backpack?  Example If we have 4 ...

Given two strings, find the longest common substring. Return the length of it. Example Given  A="ABCD" ,  B="CBCE...

Given two strings, find the longest comment subsequence (LCS). Your code should return the length of LCS. Example For "ABCD...

Given a sequence of integers, find the longest increasing subsequence (LIS). You code should return the length of the LIS. Example F...

Given two values k1 and k2 (where k1 < k2) and a root pointer to a Binary Search Tree. Find all the keys of tree in range k1 to k2. i.e....

Given the root and two nodes in a Binary Tree. Find the lowest common ancestor(LCA) of the two nodes. The lowest common ancestor is the n...

Given a  rotated  sorted array, recover it to sorted array in-place. Example [4, 5, 1, 2, 3]  ->  [1, 2, 3, 4, 5] Challenge ...

Write an efficient algorithm that searches for a value in an m x n matrix, return the occurrence of it. This matrix has the following pro...

The code base version is an integer and start from 1 to n. One day, someone commit a bad version in the code case, so it caused itself and ...