add a solution for 417

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_417.java

@@ -1,7 +1,10 @@
 package com.fishercoder.solutions;
 
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
 import java.util.List;
+import java.util.Queue;
 
 public class _417 {
     public static class Solution1 {
@@ -57,4 +60,64 @@ void dfs(int[][] matrix, boolean[][] visited, int height, int x, int y) {
         }
     }
 
+    public static class Solution2 {
+        public List<List<Integer>> pacificAtlantic(int[][] matrix) {
+            List<List<Integer>> result = new ArrayList<>();
+            if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
+                return result;
+            }
+            int m = matrix.length;
+            int n = matrix[0].length;
+            for (int i = 0; i < m; i++) {
+                for (int j = 0; j < n; j++) {
+                    boolean[] touchesPacificAndAtlantic = new boolean[2];
+                    update(i, j, m, n, touchesPacificAndAtlantic);
+                    Queue<int[]> queue = new LinkedList<>();
+                    boolean[][] visited = new boolean[m][n];
+                    visited[i][j] = true;
+                    queue.offer(new int[]{i, j});
+                    if (bfs(matrix, m, n, touchesPacificAndAtlantic, queue, visited)) {
+                        result.add(new ArrayList<>(Arrays.asList(i, j)));
+                    }
+                }
+            }
+            return result;
+        }
+
+        private void update(int i, int j, int m, int n, boolean[] touchesPacificAndAtlantic) {
+            if (i == 0 || j == 0) {
+                touchesPacificAndAtlantic[0] = true;
+            }
+            if (i == m - 1 || j == n - 1) {
+                touchesPacificAndAtlantic[1] = true;
+            }
+        }
+
+        private boolean bfs(int[][] matrix, int m, int n, boolean[] touchesPacificAndAtlantic, Queue<int[]> queue, boolean[][] visited) {
+            if (touchesPacificAndAtlantic[0] && touchesPacificAndAtlantic[1]) {
+                return true;
+            }
+            int[] directions = new int[]{0, 1, 0, -1, 0};
+            while (!queue.isEmpty()) {
+                int size = queue.size();
+                for (int k = 0; k < size; k++) {
+                    int[] curr = queue.poll();
+                    for (int p = 0; p < directions.length - 1; p++) {
+                        int newx = curr[0] + directions[p];
+                        int newy = curr[1] + directions[p + 1];
+                        if (newx >= 0 && newx < m && newy >= 0 && newy < n && matrix[newx][newy] <= matrix[curr[0]][curr[1]] && !visited[newx][newy]) {
+                            visited[newx][newy] = true;
+                            queue.offer(new int[]{newx, newy});
+                            update(newx, newy, m, n, touchesPacificAndAtlantic);
+                            if (touchesPacificAndAtlantic[0] && touchesPacificAndAtlantic[1]) {
+                                return true;
+                            }
+                        }
+                    }
+                }
+            }
+            return false;
+        }
+    }
+
 }