number_of_islands

Author: hitzzc

README.md

@@ -158,6 +158,7 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [191. Number of 1 Bits](https://github.com/hitzzc/go-leetcode/tree/master/number_of_1bits)
 #### [198. House Robber](https://github.com/hitzzc/go-leetcode/tree/master/house_robber)
 #### [199. Binary Tree Right Side View](https://github.com/hitzzc/go-leetcode/tree/master/binary_tree_right_side_view)
+#### [200. Number of Islands](https://github.com/hitzzc/go-leetcode/tree/master/number_of_islands)
 
 
 

number_of_islands/number_of_islands.go

@@ -0,0 +1,61 @@
+package number_of_islands
+
+func numIslands(grid [][]byte) int {
+	if len(grid) == 0 || len(grid[0]) == 0 {
+		return 0
+	}
+	var ret int
+	visited := map[int]bool{}
+	var k int
+	for i := range grid {
+		for j := range grid[i] {
+			if grid[i][j] == '0' {
+				continue
+			}
+			k = hash(i, j, len(grid[0]))
+			if _, ok := visited[k]; ok {
+				continue
+			}
+			ret++
+			queue := []int{k}
+			for len(queue) != 0 {
+				top := queue[0]
+				queue = queue[1:]
+				row, col := top/len(grid[0]), top%len(grid[0])
+				if row > 0 && grid[row-1][col] == '1' {
+					k = hash(row-1, col, len(grid[0]))
+					if _, ok := visited[k]; !ok {
+						queue = append(queue, k)
+						visited[k] = true
+					}
+				}
+				if row < len(grid)-1 && grid[row+1][col] == '1' {
+					k = hash(row+1, col, len(grid[0]))
+					if _, ok := visited[k]; !ok {
+						queue = append(queue, k)
+						visited[k] = true
+					}
+				}
+				if col > 0 && grid[row][col-1] == '1' {
+					k = hash(row, col-1, len(grid[0]))
+					if _, ok := visited[k]; !ok {
+						queue = append(queue, k)
+						visited[k] = true
+					}
+				}
+				if col < len(grid[0])-1 && grid[row][col+1] == '1' {
+					k = hash(row, col+1, len(grid[0]))
+					if _, ok := visited[k]; !ok {
+						queue = append(queue, k)
+						visited[k] = true
+					}
+				}
+			}
+		}
+	}
+	return ret
+}
+
+func hash(row, col, length int) int {
+	return row*length + col
+}