add 461

fishercoder1534 · fishercoder1534 · commit b9d92aabba45 · 2021-10-04T10:35:47.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_463.java b/src/main/java/com/fishercoder/solutions/_463.java
@@ -1,5 +1,8 @@
 package com.fishercoder.solutions;
 
+import java.util.LinkedList;
+import java.util.Queue;
+
 public class _463 {
 
     public static class Solution1 {
@@ -27,4 +30,46 @@ public int islandPerimeter(int[][] grid) {
             return count;
         }
     }
+
+    public static class Solution2 {
+        /**
+         * My completely original solution on 10/4/2021:
+         * Count the number of island neighbors that each island has, then reduce this number from four and add it to the result.
+         */
+        public int islandPerimeter(int[][] grid) {
+            int perimeter = 0;
+            int m = grid.length;
+            int n = grid[0].length;
+            boolean[][] visited = new boolean[m][n];
+            int[] directions = new int[]{0, 1, 0, -1, 0};
+            for (int i = 0; i < m; i++) {
+                for (int j = 0; j < n; j++) {
+                    if (grid[i][j] == 1) {
+                        Queue<int[]> queue = new LinkedList<>();
+                        queue.offer(new int[]{i, j});
+                        while (!queue.isEmpty()) {
+                            int[] curr = queue.poll();
+                            if (!visited[curr[0]][curr[1]]) {
+                                visited[curr[0]][curr[1]] = true;
+                                int neighborCount = 0;
+                                for (int k = 0; k < directions.length - 1; k++) {
+                                    int newX = curr[0] + directions[k];
+                                    int newY = curr[1] + directions[k + 1];
+                                    if (newX >= 0 && newX < m && newY >= 0 && newY < n && grid[newX][newY] == 1) {
+                                        neighborCount++;
+                                        if (!visited[newX][newY]) {
+                                            queue.offer(new int[]{newX, newY});
+                                        }
+                                    }
+                                }
+                                perimeter += 4 - neighborCount;
+                            }
+                        }
+                        return perimeter;
+                    }
+                }
+            }
+            return perimeter;
+        }
+    }
 }
