1254. Number of Closed Islands(amend commit msg test)

Author: BGMer7

src/com/gatsby/_1254NumberOfClosedIslands.java

@@ -0,0 +1,30 @@
+package com.gatsby;
+
+public class _1254NumberOfClosedIslands {
+    private int[][] isVisited;
+    int row;
+    int col;
+    int res;
+
+    private boolean dfs(int i, int j) {
+        if (i < 0 || j < 0 || i >= row || j >= col) return false; // 和边界接壤，实际上不属于被包围
+        if (isVisited[i][j] == 1) return true;
+        isVisited[i][j] = 1;
+        // 不能使用&&因为我们需要在每一次遍历中都把所有的格子都标记，但是如果使用&&，一旦前提条件不符合，后面的dfs就不会执行了
+        return dfs(i - 1, j) & dfs(i, j - 1) & dfs(i + 1, j) & dfs(i, j + 1);
+    }
+
+
+    public int closedIsland(int[][] grid) {
+        this.row = grid.length;
+        this.col = grid[0].length;
+        this.isVisited = grid;
+        for (int i = 0; i < row; ++i) {
+            for (int j = 0; j < col; ++j) {
+                if (isVisited[i][j] == 0 && dfs(i, j))
+                    res++;
+            }
+        }
+        return res;
+    }
+}