number of distinct islands using direction to create a DFS path taken string

Author: Arjiit

DFS/numDistinctIslands.java

@@ -0,0 +1,31 @@
+class Solution {
+    // S - start, U - Up, D - Down, O- out of bound/0, R- Right, L-Left
+    public int numDistinctIslands(int[][] grid) {
+        if (grid == null || grid.length == 0) {
+            return 0;
+        }
+        HashSet<String> set = new HashSet<>();
+        for (int i=0; i<grid.length; i++) {
+            for (int j=0; j<grid[0].length; j++) {
+                if (grid[i][j] == 1) {
+                String island = dfs(grid, i, j, grid.length, grid[0].length, "S"); 
+                    set.add(island);
+                }
+            }
+        }
+        return set.size();
+    }
+    
+    public String dfs(int[][] grid, int row, int col, int m, int n, String dir) {
+        if (row < 0 || row >= grid.length || col < 0 || col >= grid[0].length || grid[row][col] == 0) {
+            return "O";
+        }
+        grid[row][col] = 0;
+        String left = dfs(grid, row, col-1, m, n, "L");
+        String up = dfs(grid, row-1, col, m, n, "U");
+        String down = dfs(grid, row+1, col, m, n, "D");
+        String right = dfs(grid, row, col+1, m, n, "R");
+        
+        return dir + left + up + down + right;
+    }
+}