Grid & Matrix

Many problems hand you a 2D grid and ask you to explore it, as in Number of Islands or Rotting Oranges. Treat each cell as a node with up to four neighbors and the usual search methods apply.

The four chapters cover DFS on grids, BFS on grids, 0-1 BFS for moves that cost either zero or one, and problems that combine them. It is a short plan that sits between trees and graph algorithms on the route.

47 problemsRating 1461–25824 Chapters

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I. Grid DFS

§1.1 Fundamentals

Problem	Rating
200. Number of Islands	Unrated
695. Max Area of Island	Unrated
3619. Count Islands with Total Value Divisible by K	1461
463. Island Perimeter	Unrated
2658. Maximum Number of Fish in a Grid	1490
733. Flood Fill	Unrated
1034. Coloring a Border	1579
1020. Number of Enclaves	1615
2684. Maximum Number of Moves in a Grid	1626
1254. Number of Closed Islands	1659
130. Surrounded Regions	Unrated
1905. Count Sub Islands	1679
1391. Check If There Is a Valid Path in a Grid	1746
417. Pacific Atlantic Water Flow	Unrated
529. Minesweeper	Unrated
1559. Detect Cycles in 2D Grid	1838
827. Making a Large Island	1934

II. Grid BFS

§2.1 Fundamentals

Problem	Rating
1926. Nearest Exit From Entrance in Maze	1638
1091. Shortest Path in Binary Matrix	1658
1162. As Far From Land As Possible	1666
542. 01 Matrix	Unrated
994. Rotting Oranges	Unrated
1765. Map of Highest Peak	1783
934. Shortest Bridge	1826
2146. K Highest Ranked Items Within a Price Range	1837
1293. Shortest Path in a Grid with Obstacles Elimination	1967
909. Snakes AND Ladders	2020
1210. Minimum Moves to Reach Target with Rotations	2022
675. Cut Off Trees for Golf Event	Unrated
2812. Find the Safest Path in a Grid	2154
749. Contain Virus	2277

III. Grid 0-1 BFS

§3.1 Fundamentals

Problem	Rating
3286. Find a Safe Walk Through a Grid	Unrated
2290. Minimum Obstacle Removal to Reach Corner	2138
1368. Minimum Cost to Make at Least One Valid Path in a Grid	2069
3552. Grid Teleportation Traversal	2036
1824. Minimum Sideway Jumps	Unrated

IV. Comprehensive Grid Applications

§5.1 Classic Problems

Problem	Rating
1631. Path with Minimum Effort	1948
778. Swim in Rising Water	2097
329. Longest Increasing Path in a Matrix	Unrated
3568. Minimum Moves to Clean the Classroom	2143
1036. Escape a Large Maze	2165
864. Shortest Path to Get All Keys	2259
1263. Minimum Moves to Move a Box to Their Target Location	2297
2258. Escape the Spreading Fire	2347
2556. Disconnect Path in a Binary Matrix by at Most One Flip	2369
2577. Minimum Time to Visit a Cell in a Grid	2382
2617. Minimum Number of Visited Cells in a Grid	2582

It is the second plan on Track 2, after Linked Lists, Trees & Backtracking, and your heroine brings its problems in order, one unsolved problem at a time.

Ratings come from zerotrac's LeetCode contest ratings. Some problems have no zerotrac rating and are marked Unrated.

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