Update 0200.岛屿数量.广搜版.md for golang

problems/0200.岛屿数量.广搜版.md

@@ -199,7 +199,9 @@ class Solution {
 
 
 ### Python
+
 BFS solution 
+
 ```python
 class Solution:
     def __init__(self):
@@ -240,6 +242,7 @@ class Solution:
 
 ```
 ### JavaScript
+
 ```javascript
 var numIslands = function (grid) {
     let dir = [[0, 1], [1, 0], [-1, 0], [0, -1]]; // 四个方向
@@ -321,11 +324,53 @@ function numIslands2(grid: string[][]): number {
 }
 ```
 
+### Go
+
+```go
+var DIRECTIONS = [4][2]int{{-1, 0}, {0, -1}, {1, 0}, {0, 1}}
+
+func numIslands(grid [][]byte) int {
+	res := 0
+
+	visited := make([][]bool, len(grid))
+	for i := 0; i < len(grid); i++ {
+		visited[i] = make([]bool, len(grid[0]))
+	}
+
+	for i, rows := range grid {
+		for j, v := range rows {
+			if v == '1' && !visited[i][j] {
+				res++
+				bfs(grid, visited, i, j)
+			}
+		}
+	}
+	return res
+}
+
+func bfs(grid [][]byte, visited [][]bool, i, j int) {
+	queue := [][2]int{{i, j}}
+	visited[i][j] = true // 标记已访问，循环中标记会导致重复
+	for len(queue) > 0 {
+		cur := queue[0]
+		queue = queue[1:]
+		for _, d := range DIRECTIONS {
+			x, y := cur[0]+d[0], cur[1]+d[1]
+			if x < 0 || x >= len(grid) || y < 0 || y >= len(grid[0]) {
+				continue
+			}
+			if grid[x][y] == '1' && !visited[x][y] {
+				visited[x][y] = true
+				queue = append(queue, [2]int{x, y})
+			}
+		}
+	}
+}
+```
 
 ### Rust
 
 ```rust
-
 use std::collections::VecDeque;
 impl Solution {
     const DIRECTIONS: [(i32, i32); 4] = [(0, 1), (1, 0), (-1, 0), (0, -1)];