Merge pull request #2151 from Lozakaka/patch-34

新增java解法
2025-07-06 23:28:29 +08:00 · 2023-07-14 09:59:21 +08:00
parent b8a677f450 2b3ce44535
commit 70150880eb
1 changed files with 124 additions and 2 deletions
--- a/problems/1020.飞地的数量.md
+++ b/problems/1020.飞地的数量.md
@ -149,7 +149,63 @@ public:

 ### Java

-深度优先遍历版本：
+深度优先遍历(没有终止条件 + 空間優化（淹沒島嶼，沒有使用visited數組）)
+```java
+//DFS
+class Solution {
+    int count = 0;
+    int[][] dir ={
+        {0, 1},
+        {1, 0},
+        {-1, 0},
+        {0, -1}
+    };
+    private void dfs(int[][] grid, int x, int y){
+        if(grid[x][y] == 0)
+            return;
+        
+        grid[x][y] = 0;
+        count++;
+
+        for(int i = 0; i < 4; i++){
+            int nextX = x + dir[i][0];
+            int nextY = y + dir[i][1];
+
+            if(nextX < 0 || nextY < 0 || nextX >= grid.length || nextY >= grid[0].length)
+                continue;
+            dfs(grid, nextX, nextY);
+        }
+        
+    }
+
+    public int numEnclaves(int[][] grid) {
+        for(int i = 0; i < grid.length; i++){
+            if(grid[i][0] == 1)
+                dfs(grid, i, 0);
+            if(grid[i][grid[0].length - 1] == 1)
+                dfs(grid, i, grid[0].length - 1);
+        }
+        //初始化的時候，j 的上下限有調整過，必免重複操作。
+        for(int j = 1; j < grid[0].length - 1; j++){
+            if(grid[0][j] == 1)
+                dfs(grid, 0, j);
+            if(grid[grid.length - 1][j] == 1)
+                dfs(grid, grid.length - 1, j);
+        }
+        count = 0;
+
+        for(int i = 1; i < grid.length - 1; i++){
+            for(int j = 1; j < grid[0].length - 1; j++){
+                if(grid[i][j] == 1)
+                    dfs(grid, i, j);
+            }
+        }
+        return count;
+    }
+}
+```
+
+深度优先遍历(没有终止条件)

 ```java
 class Solution {
@ -206,7 +262,7 @@ class Solution {
 }
 ```

-广度优先遍历版本：
+广度优先遍历（使用visited數組）

 ```java
 class Solution {
@ -269,6 +325,72 @@ class Solution {
 }
 ```

+廣度优先遍历(空間優化（淹沒島嶼，沒有使用visited數組）)
+```java
+//BFS
+class Solution {
+    int count = 0;
+    int[][] dir ={
+        {0, 1},
+        {1, 0},
+        {-1, 0},
+        {0, -1}
+    };
+    private void bfs(int[][] grid, int x, int y){
+        Queue<Integer> que = new LinkedList<>();
+        que.offer(x);
+        que.offer(y);
+        count++;
+        grid[x][y] = 0;
+        
+        while(!que.isEmpty()){
+            int currX = que.poll();
+            int currY = que.poll();
+
+            for(int i = 0; i < 4; i++){
+                int nextX = currX + dir[i][0];
+                int nextY = currY + dir[i][1];
+
+                if(nextX < 0 || nextY < 0 || nextX >= grid.length || nextY >= grid[0].length)
+                    continue;
+
+                if(grid[nextX][nextY] == 1){
+                    que.offer(nextX);
+                    que.offer(nextY);
+                    count++;
+                    grid[nextX][nextY] = 0;
+                }
+            }
+        }
+    }
+
+    public int numEnclaves(int[][] grid) {
+        for(int i = 0; i < grid.length; i++){
+            if(grid[i][0] == 1)
+                bfs(grid, i, 0);
+            if(grid[i][grid[0].length - 1] == 1)
+                bfs(grid, i, grid[0].length - 1);
+        }
+        for(int j = 1; j < grid[0].length; j++){
+            if(grid[0][j] == 1)
+                bfs(grid, 0 , j);
+            if(grid[grid.length - 1][j] == 1)
+                bfs(grid, grid.length - 1, j);
+        }
+        count = 0;
+        for(int i = 1; i < grid.length - 1; i++){
+            for(int j = 1; j < grid[0].length - 1; j++){
+                if(grid[i][j] == 1)
+                    bfs(grid,i ,j);
+            }
+        }
+        return count;
+    }
+}
+
+
+```
+
 ### Python

 深度优先遍历