Flood Fill
BFS & DFS Problems DSA practice problem on Onlearn.
Difficulty: hard.
Topics: Flood Fill Algorithm in a 2-D Image Matrix, Connected Components, Graph Traversal, Depth-First Search, Breadth-First Search, Recursion, Matrices, Two-dimensional Array Traversal, Time Complexity, Space Complexity, Arrays, space complexity, graph algorithms, graph components, dfs, graph traversal, time complexity analysis, grid traversal, recursion, bfs, Number of Islands / Flood Fill.
An image is represented by a 2 D array of integers, each integer representing the pixel value of the image. Given a coordinate (sr, sc) representing the starting pixel (row and column) of the flood fill, and a pixel value newColor, "flood fill" the image. To perform a "flood fill", consider the starting pixel, plus any pixels connected 4 directionally to the starting pixel of the same color as the starting pixel, plus any pixels connected 4 directionally to those pixels (also with the same color as the starting pixel), and so on. Replace the color of all of the aforementioned pixels with the newColor. Return the modified image after the flood fill. Input: The input consists of: A 2D array of integers image representing the pixel values. An integer sr, the starting row. An integer sc, the starting column. An integer newColor, the new color to apply. Output: The modified 2D array image after applying the flood fill. Example: Input: sr = 1, sc = 1, newColor = 2 image = [ [1,1,1], [1,1,0], [1,0,1] ] Output: [ [2,2,2], [2,2,0], [2,0,1] ] Explanation: From the center of the image (with position (sr, sc) = (1, 1)), all pixels connected by a path of the same color as the starting pixel are colored with the new color. Note the bottom corner is not colored 2, because it is not 4 directionally connected to the starting pixel.