As a solo warrior in OJ, I spent about nearly 50% of my time on tackling TLE - that is innumerous hours. I almost lost my courage to OJ.But thanks to this post: http://www.spoj.com/forum/viewtopic.php?f=3&t=7968. I didn't use all of the hints, but ge…
Total Accepted: 31557 Total Submissions: 116793 Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below. [ [2], [3,4], [6,5,7], [4,1,8,3] ] The minimum path sum from top to botto…
Problem Link: http://oj.leetcode.com/problems/word-ladder-ii/ Basically, this problem is same to Word Ladder I, which uses a double-direction BFS. However, the difference is that we need to keep track of all paths during the double-direction BFS in o…
Problem Link: http://oj.leetcode.com/problems/best-time-to-buy-and-sell-stock-iii/ Linear Time Solution We try to solve this problem in O(n) time in the help of the algorithm in Best Time to Buy and Sell Stock, which can return the max profit by give…
Problem Link: http://oj.leetcode.com/problems/best-time-to-buy-and-sell-stock/ We solve this problem using DP algorithm, which only scans the prices list once. So the algorithm is in O(n) where n is the length of prices list. By given a list prices[0…
Problem Link: http://oj.leetcode.com/problems/surrounded-regions/ We can do follows in the 2D board. Use BFS from all 'O' cells on the boundary and mark all connected 'O' cells Scan the board and flip all unmarked 'O' to 'X'. The following code is py…
Problem Link: http://oj.leetcode.com/problems/palindrome-partitioning-ii/ We solve this problem by using Dynamic Programming. Optimal Sub-structure Assume a string S has the palindrome minimum cuts n, and S = W1 + W2 + ... + Wn where Wi is a palindro…
Problem Link: http://oj.leetcode.com/problems/palindrome-partitioning/ We solve this problem using Dynamic Programming. The problem holds the property of optimal sub-strcuture. Assume S is a string that can be partitioned into palindromes w1, ..., wn…
Problem Link: http://oj.leetcode.com/problems/valid-palindrome/ The following two conditions would simplify the problem: only alphanumerci characters considered ignoring cases Given a string, we check if it is a valid palindrome by following rules: A…
Problem link: http://oj.leetcode.com/problems/candy/ Suppose we are given an array R[1..N] that are ratings of N children. Let C[1..N] be a new array where C[i] is the number of candies for i-th child. From the description, C[i] should meet following…
There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an e…
Remember the story of Little Match Girl? By now, you know exactly what matchsticks the little match girl has, please find out a way you can make one square by using up all those matchsticks. You should not break any stick, but you can link them up, a…
Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possible sentences. For example, givens = "catsanddog",dict = ["cat", "cats"…
Unique Paths A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked…
You are given K eggs, and you have access to a building with N floors from 1 to N. Each egg is identical in function, and if an egg breaks, you cannot drop it again. You know that there exists a floor F with 0 <= F <= N such that any egg dropped at…
作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 前缀是否回文 判断前缀 相似题目 参考资料 日期 题目地址:https://leetcode.com/problems/shortest-palindrome/description/ 题目描述 Given a string s, you are allowed to convert it to a palindrome by adding char…
Total Accepted: 12400 Total Submissions: 83230 Compare two version numbers version1 and version2. If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0. You may assume that the version strings are non-empty and co…
Total Accepted: 3790 Total Submissions: 21072 All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA. W…
Problem Link: http://oj.leetcode.com/problems/word-ladder/ Two typical techniques are inspected in this problem: Hash Table. One hash set is the words dictionary where we can check if a word is in the dictionary in O(1) time. The other hash set is us…
Problem Link: https://oj.leetcode.com/problems/validate-binary-search-tree/ We inorder-traverse the tree, and for each node we check if current_node.val > prev_node.val. The code is as follows. # Definition for a binary tree node # class TreeNode: #…
Problem Link: https://oj.leetcode.com/problems/recover-binary-search-tree/ We know that the inorder traversal of a binary search tree should be a sorted array. Therefore, we can compare each node with its previous node in the inorder to find the two…
Problem Link: https://oj.leetcode.com/problems/same-tree/ The following recursive version is accepted but the iterative one is not accepted... # Definition for a binary tree node # class TreeNode: # def __init__(self, x): # self.val = x # self.left =…
Problem Link: https://oj.leetcode.com/problems/symmetric-tree/ To solve the problem, we can traverse the tree level by level. For each level, we construct an array of values of the length 2^depth, and check if this array is symmetric. The tree is sym…
Problem Link: https://oj.leetcode.com/problems/binary-tree-level-order-traversal/ Traverse the tree level by level using BFS method. # Definition for a binary tree node # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # se…
Problem Link: https://oj.leetcode.com/problems/binary-tree-zigzag-level-order-traversal/ Just BFS from the root and for each level insert a list of values into the result. # Definition for a binary tree node # class TreeNode: # def __init__(self, x):…
