diff --git a/102_binary_tree_level_order_traversal/bst_bfs.c b/102_binary_tree_level_order_traversal/bst_bfs.c
index 4daacf5..ba1664a 100644
--- a/102_binary_tree_level_order_traversal/bst_bfs.c
+++ b/102_binary_tree_level_order_traversal/bst_bfs.c
@@ -41,18 +41,6 @@ list_empty(const struct list_head *head)
     return (head->next == head);
 }
 
-static inline int
-list_is_first(const struct list_head *list, const struct list_head *head)
-{
-    return list->prev == head;
-}
-
-static inline int
-list_is_last(const struct list_head *list, const struct list_head *head)
-{
-    return list->next == head;
-}
-
 static inline void
 __list_add(struct list_head *new, struct list_head *prev, struct list_head *next)
 {
diff --git a/130_surrounded_regions/Makefile b/130_surrounded_regions/Makefile
new file mode 100644
index 0000000..0743ff4
--- /dev/null
+++ b/130_surrounded_regions/Makefile
@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test surrounded_regions.c
diff --git a/130_surrounded_regions/surrounded_regions.c b/130_surrounded_regions/surrounded_regions.c
new file mode 100644
index 0000000..96f2ca4
--- /dev/null
+++ b/130_surrounded_regions/surrounded_regions.c
@@ -0,0 +1,241 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#define container_of(ptr, type, member) \
+    ((type *)((char *)(ptr) - (size_t)&(((type *)0)->member)))
+
+#define list_entry(ptr, type, member) \
+    container_of(ptr, type, member)
+
+#define	list_first_entry(ptr, type, field)  list_entry((ptr)->next, type, field)
+#define	list_last_entry(ptr, type, field)  list_entry((ptr)->prev, type, field)
+
+#define	list_for_each(p, head) \
+	for (p = (head)->next; p != (head); p = p->next)
+
+#define	list_for_each_safe(p, n, head) \
+	for (p = (head)->next, n = p->next; p != (head); p = n, n = p->next)
+
+struct list_head {
+    struct list_head *next, *prev;
+};
+
+static inline void
+INIT_LIST_HEAD(struct list_head *list)
+{
+    list->next = list->prev = list;
+}
+
+static inline int
+list_empty(const struct list_head *head)
+{
+    return (head->next == head);
+}
+
+static inline void
+__list_add(struct list_head *new, struct list_head *prev, struct list_head *next)
+{
+    next->prev = new;
+    new->next = next;
+    new->prev = prev;
+    prev->next = new;
+}
+
+static inline void
+list_add(struct list_head *_new, struct list_head *head)
+{
+    __list_add(_new, head, head->next);
+}
+
+static inline void
+list_add_tail(struct list_head *_new, struct list_head *head)
+{
+    __list_add(_new, head->prev, head);
+}
+
+static inline void
+__list_del(struct list_head *entry)
+{
+    entry->next->prev = entry->prev;
+    entry->prev->next = entry->next;
+}
+
+static inline void
+list_del(struct list_head *entry)
+{
+    __list_del(entry);
+    entry->next = entry->prev = NULL;
+}
+
+struct node {
+    struct list_head link;
+    int x, y;
+};
+
+static struct node *node_new(struct list_head *free_list)
+{
+    struct node *new;
+    if (list_empty(free_list)) {
+        new = malloc(sizeof(*new));
+    } else {
+        new = list_first_entry(free_list, struct node, link);
+        list_del(&new->link);
+    }
+    return new;
+}
+
+static void bfs(char **board, int row_size, int col_size,
+                struct list_head *queue, struct list_head *free_list)
+{
+    while (!list_empty(queue)) {
+        struct node *new;
+        struct node *node = list_first_entry(queue, struct node, link);
+        board[node->x][node->y] = 'P';
+
+        if (node->x > 0 && board[node->x - 1][node->y] == 'O') {
+            new = node_new(free_list);
+            new->x = node->x - 1;
+            new->y = node->y;
+            board[new->x][new->y] = 'P';
+            list_add_tail(&new->link, queue);
+        }
+
+        if (node->y < col_size - 1 && board[node->x][node->y + 1] == 'O') {
+            new = node_new(free_list);
+            new->x = node->x;
+            new->y = node->y + 1;
+            board[new->x][new->y] = 'P';
+            list_add_tail(&new->link, queue);
+        }
+
+        if (node->x < row_size - 1 && board[node->x + 1][node->y] == 'O') {
+            new = node_new(free_list);
+            new->x = node->x + 1;
+            new->y = node->y;
+            board[new->x][new->y] = 'P';
+            list_add_tail(&new->link, queue);
+        }
+
+        if (node->y > 0 && board[node->x][node->y - 1] == 'O') {
+            new = node_new(free_list);
+            new->x = node->x;
+            new->y = node->y - 1;
+            board[new->x][new->y] = 'P';
+            list_add_tail(&new->link, queue);
+        }
+
+        list_del(&node->link);
+        list_add(&node->link, free_list);
+    } 
+}
+
+void solve(char** board, int boardRowSize, int boardColSize)
+{
+    int i, j;
+    struct node *new;
+    struct list_head queue, free_list;
+
+    INIT_LIST_HEAD(&queue);
+    INIT_LIST_HEAD(&free_list);
+
+    for (i = 0; i < boardColSize; i++) {
+        if (board[0][i] == 'O') {
+            new = node_new(&free_list);
+            new->x = 0;
+            new->y = i;
+            list_add_tail(&new->link, &queue);
+            bfs(board, boardRowSize, boardColSize, &queue, &free_list);
+        }
+    }
+
+    for (i = 0; i < boardColSize; i++) {
+        if (board[boardRowSize - 1][i] == 'O') {
+            new = node_new(&free_list);
+            new->x = boardRowSize - 1;
+            new->y = i;
+            list_add_tail(&new->link, &queue);
+            bfs(board, boardRowSize, boardColSize, &queue, &free_list);
+        }
+    }
+
+    for (i = 0; i < boardRowSize; i++) {
+        if (board[i][0] == 'O') {
+            new = node_new(&free_list);
+            new->x = i;
+            new->y = 0;
+            list_add_tail(&new->link, &queue);
+            bfs(board, boardRowSize, boardColSize, &queue, &free_list);
+        }
+    }
+
+    for (i = 0; i < boardRowSize; i++) {
+        if (board[i][boardColSize - 1] == 'O') {
+            new = node_new(&free_list);
+            new->x = i;
+            new->y = boardColSize - 1;
+            list_add_tail(&new->link, &queue);
+            bfs(board, boardRowSize, boardColSize, &queue, &free_list);
+        }
+    }
+
+    for (i = 0; i < boardRowSize; i++) {
+        for (j = 0; j < boardColSize; j++) {
+            board[i][j] = board[i][j] == 'P' ? 'O' : 'X';
+        }
+    }
+}
+
+int main(void)
+{
+    int i, j;
+    int row_size = 5;
+    int col_size = 5;
+    char **board = malloc(row_size * sizeof(char *));
+    board[0] = malloc(col_size);
+    board[0][0] = 'X';
+    board[0][1] = 'X';
+    board[0][2] = 'X';
+    board[0][3] = 'X';
+    board[0][4] = 'X';
+    board[1] = malloc(col_size);
+    board[1][0] = 'O';
+    board[1][1] = 'X';
+    board[1][2] = 'O';
+    board[1][3] = 'O';
+    board[1][4] = 'X';
+    board[2] = malloc(col_size);
+    board[2][0] = 'O';
+    board[2][1] = 'O';
+    board[2][2] = 'X';
+    board[2][3] = 'O';
+    board[2][4] = 'X';
+    board[3] = malloc(col_size);
+    board[3][0] = 'X';
+    board[3][1] = 'X';
+    board[3][2] = 'O';
+    board[3][3] = 'X';
+    board[3][4] = 'X';
+    board[4] = malloc(col_size);
+    board[4][0] = 'X';
+    board[4][1] = 'X';
+    board[4][2] = 'O';
+    board[4][3] = 'O';
+    board[4][4] = 'X';
+
+    for (i = 0; i < row_size; i++) {
+        for (j = 0; j < col_size; j++) {
+            printf("%c ", board[i][j]);
+        }
+        printf("\n");
+    }
+    printf("\n");
+
+    solve(board, row_size, col_size);
+    for (i = 0; i < row_size; i++) {
+        for (j = 0; j < col_size; j++) {
+            printf("%c ", board[i][j]);
+        }
+        printf("\n");
+    }
+}