complete number of islands

Author: freefcw

leetcode/number-of-islands.go

@@ -8,16 +8,51 @@ var (
 	height int
 )
 
+const (
+	unVisited = 0
+	visited   = 1
+)
+
+var visitedMark [][]int
+
 func numIslands(grid [][]byte) int {
 	height = len(grid)
 	if height == 0 {
 		return 0
 	}
 	width = len(grid[0])
+	visitedMark = make([][]int, height)
+	for i := 0; i < height; i++ {
+		visitedMark[i] = make([]int, width)
+	}
 	total = 0
+
+	for i := 0; i < height; i++ {
+		for k := 0; k < width; k++ {
+			if grid[i][k] == '1' && visitedMark[i][k] == unVisited {
+				dfs(grid, i, k)
+				total++
+			}
+		}
+	}
+
 	return total
 }
 
-func dfs(grid [][]int, x, y int) {
+func dfs(grid [][]byte, x, y int) {
+	if x == height || y == width || x < 0 || y < 0 {
+		return
+	}
+	if visitedMark[x][y] == visited {
+		return
+	}
+	visitedMark[x][y] = visited
+	if grid[x][y] == '0' {
+		return
+	}
 
+	dfs(grid, x-1, y)
+	dfs(grid, x, y-1)
+	dfs(grid, x+1, y)
+	dfs(grid, x, y+1)
 }

leetcode/number-of-islands_test.go

@@ -9,18 +9,18 @@ func Test_numIsLands(t *testing.T) {
 	}{
 		{
 			input: [][]byte{
-				[]byte{1, 1, 1, 1, 0},
-				[]byte{1, 1, 0, 1, 0},
-				[]byte{1, 1, 0, 0, 0},
-				[]byte{0, 0, 0, 0, 0},
+				[]byte{'1', '1', '1', '1', '0'},
+				[]byte{'1', '1', '0', '1', '0'},
+				[]byte{'1', '1', '0', '0', '0'},
+				[]byte{'0', '0', '0', '0', '0'},
 			},
 			expect: 1,
 		}, {
 			input: [][]byte{
-				[]byte{1, 1, 0, 0, 0},
-				[]byte{1, 1, 0, 0, 0},
-				[]byte{0, 0, 1, 0, 0},
-				[]byte{0, 0, 0, 1, 1},
+				[]byte{'1', '1', '0', '0', '0'},
+				[]byte{'1', '1', '0', '0', '0'},
+				[]byte{'0', '0', '1', '0', '0'},
+				[]byte{'0', '0', '0', '1', '1'},
 			},
 			expect: 3,
 		},