Number of distinct islands leetcode

Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. Count the number of distinct islands. An island is considered to be the same as another if and only if one island can be translated (and not rotated or reflected) to equal the other. Example 1: 11000 11000 00011 00011 Given the above grid map, return 1. Example 2: 11011 10000 00001 11011 Given the above grid map, return 3. Notice that: 11 1 and 1 11 are considered different island shapes, because we do not consider reflection / rotation. Note: The length of each dimension in the given grid does not exceed 50.

Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. Count the number of distinct islands. An island is considered to be the same as another if and only if one island can be translated (and not rotated or reflected) to equal the other. Example 1: 11000 11000 00011 00011 Given the above grid map, return 1. Example 2: 11011 10000 00001 11011 Given the above grid map, return 3. Notice that: 11 1 and 1 11 are considered different island shapes, because we do not consider reflection / rotation. Note: The length of each dimension in the given grid does not exceed 50. • • Approach #1: Hash By Local Coordinates [Accepted] Intuition and Algorithm At the beginning, we need to find every island, which we can do using a straightforward depth-first search. The hard part is deciding whether two islands are the same. Since two islands are the same if one can be translated to match another, let's translate every island so the top-left corner is (0, 0) For example, if an island is made from squares [(2, 3), (2, 4), (3, 4)], we can think of this shape as [(0, 0), (0, 1), (1, 1)] when anchored at the top-left corner. From there, we only need to check how many unique shapes there ignoring permutations (so [(0, 0), (0, 1)] is the same as [(0, 1), (1, 0)]). We use sets directly as we have showcased below, but we could have also sorted ...

• • • • Merge K sorted lists • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 159 Longest Substring with At Most Two Distinct Characters • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 305 Number of Islands II A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positions to operate, count the number of islands after each addLand operation. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water. Example: Given m = 3, n = 3, positions = [[0,0], [0,1], [1,2], [2,1]]. Initially, the 2d grid grid is filled with water. (Assume 0 represents water and 1 represents land). 0 0 0 0 0 0 0 0 0 Operation #1: addLand(0, 0) turns the water at grid[0][0] into a land. 1 0 0 0 0 0 Number of islands = 1 0 0 0 Operation #2: addLand(0, 1) turns the water at grid[0][1] into a land. 1 1 0 0 0 0 Number of islands = 1...

Formatted question description: Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. Count the number of distinct islands. An island is considered to be the same as another if and only if one island can be translated (and not rotated or reflected) to equal the other. Example 1: 11000 11000 00011 00011 Given the above grid map, return 1. Example 2: 11011 10000 00001 11011 Given the above grid map, return 3. Notice that: 11 1 and 1 11 are considered different island shapes, because we do not consider reflection / rotation. Note: The length of each dimension in the given grid does not exceed 50. Companies: Related Topics: Similar Questions: • • Solution 1. Encode Shape // OJ: https://leetcode.com/problems/number-of-distinct-islands/ // Time: O(MN) // Space: O(MN) // Ref: https://leetcode.com/problems/number-of-distinct-islands/discuss/194673/C%2B%2B-easy-to-understand class Solution ; • • • • • class Solution • // OJ: https://leetcode.com/problems/number-of-distinct-islands/ // Time: O(MN) // Space: O(MN) // Ref: https://leetcode.com/problems/number-of-distinct-islands/discuss/194673/C%2B%2B-easy-to-understand class Solution ; • class Solution : def numDistinctIslands ( self , grid : List [ List [ int ]]) -> int : def dfs ( i , j , direction , path ): grid [ i ][ j ] = 0 path . append ( str ( direction )) dirs = [ -...

• • • • • Design • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Two Pointer • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • BST • • • • Construct Binary Tree from Inorder and Postorder Traversal • • • • • • • • • Sum Root to Leaf Numbers • Hash Table • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Memoization • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • SQL • • • • • • • • • Valid Palindrome • • • • • • • • • • • • • • • • • • • • Google 20 • • 694. Number of Distinct Islands (identical) Given a non-empty 2D array gridof 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. Count the number of distinct islands. An island is considered to be the same as another if and only if one island can be translated (and not rotated or reflected) to equal the other. Example 1: 11000 11000 00011 00011 Given the above grid map, return 1. Example 2: 11011 10000 00001 11011 Given the above grid map, return 3. Notice that: 11 1 and 1 11 are considered dif...