Algo Archives - Page 19 of 23

Combinations

Nov

27

2015

Title: Combinations Source: leetcode.com Given two integers n and k, return all possible combinations of k numbers out of 1 … n. For example, If n = 4 and k = 2, a solution is: [ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ] 12345678 [ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4],] Python solution (a) Python ''' https://leetcode.com/problems/combinations/ ''' class Solution(object): def ...

Binary Tree Postorder Traversal

Nov

27

2015

Title: Binary Tree Postorder Traversal Source: leetcode.com Given a binary tree, return the postorder traversal of its nodes’ values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 12345 1 \ 2 / 3 return [3,2,1]. Note: Recursive solution is trivial, could you do it iteratively? Python solution (Iterative) Python ''' https://leetcode.com/problems/binary-tree-postorder-traversal/ ''' # ...

Binary Tree Zigzag Level Order Traversal

Nov

27

2015

Title: Binary Tree Zigzag Level Order Traversal Source: leetcode.com Given a binary tree, return the zigzag level order traversal of its nodes’ values. (ie, from left to right, then right to left for the next level and alternate between). For example: Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7 12345 ...

Binary Tree Right Side View

Nov

27

2015

Title: Binary Tree Right Side View Source: leetcode.com Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom. For example: Given the following binary tree, 1 <--- / \ 2 3 <--- \ \ 5 4 <--- 12345 ...

Word Search

Nov

27

2015

Title: Word Search Source: leetcode.com Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically neighboring. The same letter cell may not be used more than once. For example, Given board ...

Word Pattern 1

Nov

27

2015

Title: Word Pattern Source: leetcode.com Given a pattern and a string str, find if str follows the same pattern. Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str. Examples: pattern = "abba", str = "dog cat cat dog" should return true. ...

Valid Anagram

Nov

27

2015

Title: Valid Anagram Source: leetcode.com Given two strings s and t, write a function to determine if t is an anagram of s. For example, s = “anagram”, t = “nagaram”, return true. s = “rat”, t = “car”, return false. Note: You may assume the string contains only lowercase alphabets. Follow up: What if ...

Unique Paths II

Nov

27

2015

Title: Unique Paths II Source: leetcode.com Follow up for “Unique Paths”: Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the middle of a 3×3 ...

Unique Paths

Nov

27

2015

Title: Unique Paths Source: leetcode.com 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 ‘Finish’ in the ...

Unique Binary Search Trees

Nov

26

2015

Title: Unique Binary Search Trees Source: leetcode.com Given n, how many structurally unique BST’s (binary search trees) that store values 1…n? For example, Given n = 3, there are a total of 5 unique BST’s. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ ...