BinarySearch - Largest Island Area

[https://binarysearch.com/problems/Largest-Island-Area](https://binarysearch.com/problems/Largest-Island-Area) ## Problem You are given a two-dimensional integer matrix of 1s and 0s. A 1 represents land and 0 represents water, so an island is a group of 1s that are neighboring whose perimeter is surrounded by water. You can assume that the edges of the matrix are surrounded by water. Return the area of the largest island in matrix. Constraints n, m ≤ 250 where n and m are the number of rows and columns in matrix ## Solution Textbook flood fill. Search the cell with value 1 to perform dfs. For each dfs, mark all visited cells to 0 so that it won't be visited again. Compare the return value with ans and take the max one. ``` int dfs(vector>& matrix, int i, int j) { if (i < 0 || i > matrix.size() - 1 || j < 0 || j > matrix[0].size() - 1 || matrix[i][j] == 0) return 0; matrix[i][j] = 0; return 1 + dfs(matrix, i + 1, j) + dfs(matrix, i - 1, j) + dfs(matrix, i, j + 1) + dfs(matrix, i, j - 1); } int solve(vector>& matrix) { int ans = 0; for (int i = 0; i < matrix.size(); i++) { for (int j = 0; j < matrix[i].size(); j++) { if (matrix[i][j] == 1) { ans = max(ans, dfs(matrix, i, j)); } } } return ans; } ```