diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dfs/LC_1254_ClosedIsland.java b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dfs/LC_1254_ClosedIsland.java
index 32b65e4..f89ba15 100644
--- a/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dfs/LC_1254_ClosedIsland.java
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dfs/LC_1254_ClosedIsland.java
@@ -166,4 +166,33 @@ public class LC_1254_ClosedIsland {
         return find(grid, i + 1, j) & find(grid, i - 1, j) & find(grid, i, j + 1) & find(grid, i, j - 1);
     }
 
+
+    public int closedIsland4(int[][] grid) {
+        int result = 0;
+        for (int i = 0; i < grid.length; i++) {
+            for (int j = 0; j < grid[0].length; j++) {
+                if (grid[i][j] == 0 && dfs2(grid, i, j)) {
+                    result++;
+                }
+            }
+        }
+
+        return result;
+
+    }
+
+    private boolean dfs2(int[][] grid, int i, int j) {
+        //碰到1则为封闭岛屿;超出边界则为非封闭岛屿
+        if (i < 0 || j < 0 || i >= grid.length || j >= grid[0].length) {
+            return false;
+        }
+        if (grid[i][j] == 1) {
+            return true;
+        }
+        grid[i][j] = 1;
+
+
+        return dfs2(grid, i + 1, j) & dfs2(grid, i, j + 1) & dfs2(grid, i - 1, j) & dfs2(grid, i, j - 1);
+    }
+
 }
diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/singlestack/LC_503_NextGreaterElements.java b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/singlestack/LC_503_NextGreaterElements.java
index fe96130..9db9d39 100644
--- a/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/singlestack/LC_503_NextGreaterElements.java
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/singlestack/LC_503_NextGreaterElements.java
@@ -91,7 +91,7 @@ public class LC_503_NextGreaterElements {
                 stack.pop();
             }
             if (i < n) result[i] = stack.isEmpty() ? -1 : stack.peek();
-            stack.push(nums[i%n]);
+            stack.push(nums[i % n]);
         }
 
         return result;
@@ -114,4 +114,25 @@ public class LC_503_NextGreaterElements {
         return result;
 
     }
+
+
+    public int[] nextGreaterElements3(int[] nums) {
+
+        int n = nums.length;
+        ArrayDeque<Integer> stack = new ArrayDeque<>();
+
+        int[] result = new int[n];
+
+        for (int i = n * 2 - 2; i >= 0; i--) {
+            while (!stack.isEmpty() && stack.peek() <= nums[i % n]) {//寻找第一个比当前数大的数
+                stack.pop();
+            }
+            if (i < n) result[i] = stack.isEmpty() ? -1 : stack.peek();
+            stack.push(nums[i % n]);
+        }
+
+        return result;
+
+
+    }
 }