added problem 1254

Author: SHA65536

problems/problem1254/closed_islands.go

@@ -0,0 +1,50 @@
+package problem1254
+
+/*
+Given a 2D grid consists of 0s (land) and 1s (water).
+An island is a maximal 4-directionally connected group of 0s and a closed island is an island totally (all left, top, right, bottom) surrounded by 1s.
+Return the number of closed islands.
+*/
+
+const (
+	Land  = 0
+	Water = 1
+)
+
+func closedIsland(grid [][]int) int {
+	var numIslands int
+	var found = make([][]bool, len(grid))
+	for i := range grid {
+		found[i] = make([]bool, len(grid[0]))
+	}
+	for i := range grid {
+		for j := range grid[i] {
+			if grid[i][j] == Land && !found[i][j] {
+				if !discover(grid, found, i, j) {
+					numIslands++
+				}
+			}
+		}
+	}
+	return numIslands
+}
+
+func discover(grid [][]int, found [][]bool, x, y int) bool {
+	var res bool
+	if x >= len(grid) || x < 0 || y >= len(grid[0]) || y < 0 {
+		return false
+	}
+	if grid[x][y] == Water || found[x][y] {
+		return false
+	}
+	found[x][y] = true
+	res = discover(grid, found, x+1, y) || res
+	res = discover(grid, found, x, y+1) || res
+	res = discover(grid, found, x-1, y) || res
+	res = discover(grid, found, x, y-1) || res
+	return res || isRim(x, y, grid)
+}
+
+func isRim(i, j int, grid [][]int) bool {
+	return i == 0 || j == 0 || i == len(grid)-1 || j == len(grid[0])-1
+}

problems/problem1254/closed_islands_test.go

@@ -0,0 +1,55 @@
+package problem1254
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type Result struct {
+	Input    [][]int
+	Expected int
+}
+
+var Results = []Result{
+	{[][]int{
+		{1, 1, 1, 1, 1, 1, 1, 0},
+		{1, 0, 0, 0, 0, 1, 1, 0},
+		{1, 0, 1, 0, 1, 1, 1, 0},
+		{1, 0, 0, 0, 0, 1, 0, 1},
+		{1, 1, 1, 1, 1, 1, 1, 0}}, 2},
+	{[][]int{
+		{0, 0, 1, 0, 0},
+		{0, 1, 0, 1, 0},
+		{0, 1, 1, 1, 0}}, 1},
+	{[][]int{
+		{1, 1, 1, 1, 1, 1, 1},
+		{1, 0, 0, 0, 0, 0, 1},
+		{1, 0, 1, 1, 1, 0, 1},
+		{1, 0, 1, 0, 1, 0, 1},
+		{1, 0, 1, 1, 1, 0, 1},
+		{1, 0, 0, 0, 0, 0, 1},
+		{1, 1, 1, 1, 1, 1, 1}}, 2},
+	{[][]int{
+		{0, 0, 1, 1, 0, 1, 0, 0, 1, 0},
+		{1, 1, 0, 1, 1, 0, 1, 1, 1, 0},
+		{1, 0, 1, 1, 1, 0, 0, 1, 1, 0},
+		{0, 1, 1, 0, 0, 0, 0, 1, 0, 1},
+		{0, 0, 0, 0, 0, 0, 1, 1, 1, 0},
+		{0, 1, 0, 1, 0, 1, 0, 1, 1, 1},
+		{1, 0, 1, 0, 1, 1, 0, 0, 0, 1},
+		{1, 1, 1, 1, 1, 1, 0, 0, 0, 0},
+		{1, 1, 1, 0, 0, 1, 0, 1, 0, 1},
+		{1, 1, 1, 0, 1, 1, 0, 1, 1, 0}}, 5},
+}
+
+func TestClosedIslands(t *testing.T) {
+	assert := assert.New(t)
+
+	for _, res := range Results {
+		want := res.Expected
+		got := closedIsland(res.Input)
+		assert.Equal(want, got, fmt.Sprintf("%+v", res))
+	}
+}

readme.md

@@ -342,6 +342,7 @@ Each problem is in it's own directory, with test files. There are helper package
 | 1235 | [Maximum Profit in Job Scheduling](https://leetcode.com/problems/maximum-profit-in-job-scheduling/) | [My Solution](./problems/problem1235) | ✅ |
 | 1239 | [Maximum Length of a Concatenated String with Unique Characters](https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters) | [My Solution](./problems/problem1239) | ✅ |    
 | 1268 | [Search Suggestions System](https://leetcode.com/problems/search-suggestions-system) | [My Solution](./problems/problem1268) | ✅ |
+| 1254 | [Number of Closed Islands](https://leetcode.com/problems/number-of-closed-islands) | [My Solution](./problems/problem1254) | ✅ |
 | 1293 | [Shortest Path in a Grid with Obstacles Elimination](https://leetcode.com/problems/shortest-path-in-a-grid-with-obstacles-elimination) | [My Solution](./problems/problem1293) | ✅ |
 | 1302 | [Deepest Leaves Sum](https://leetcode.com/problems/deepest-leaves-sum) | [My Solution](./problems/problem1302) | ✅ |
 | 1305 | [All Elements in Two Binary Search Trees](https://leetcode.com/problems/all-elements-in-two-binary-search-trees) | [My Solution](./problems/problem1305) | ✅ |