Create 694-number-of-distinct-islands.js

Author: everthis

694-number-of-distinct-islands.js

@@ -0,0 +1,65 @@
+/**
+
+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.
+
+*/
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+const numDistinctIslands = function(grid) {
+  if (!grid.length) return 0;
+  const pattern = new Set();
+  grid.forEach((rows, row) => {
+    rows.forEach((val, col) => {
+      if (val === 1) pattern.add(depthFirst(grid, row, col, "o"));
+    });
+  });
+  return pattern.size;
+};
+
+function depthFirst(graph, row, col, di) {
+  if (graph[row] && graph[row][col]) {
+    graph[row][col] = 0;
+    let p =
+      di +
+      depthFirst(graph, row + 1, col, "d") +
+      depthFirst(graph, row - 1, col, "u") +
+      depthFirst(graph, row, col + 1, "r") +
+      depthFirst(graph, row, col - 1, "l") +
+      "b";
+    return p;
+  } else return "";
+}