Add solution and test-cases for problem 827

Author: 0xff-dev

leetcode/801-900/0827.Making-A-Large-Island/README.md

@@ -1,28 +1,35 @@
 # [827.Making A Large Island][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+You are given an `n x n` binary matrix `grid`. You are allowed to change **at most one** `0` to be `1`.
+
+Return the size of the largest **island** in `grid` after applying this operation.
+
+An **island** is a 4-directionally connected group of `1`s.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: grid = [[1,0],[0,1]]
+Output: 3
+Explanation: Change one 0 to 1 and connect two 1s, then we get an island with area = 3.
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Making A Large Island
-```go
 ```
+Input: grid = [[1,1],[1,0]]
+Output: 4
+Explanation: Change the 0 to 1 and make the island bigger, only one island with area = 4.
+```
+
+**Example 3:**
 
+```
+Input: grid = [[1,1],[1,1]]
+Output: 4
+Explanation: Can't change any 0 to 1, only one island with area = 4.
+```
 
 ## 结语
 

leetcode/801-900/0827.Making-A-Large-Island/Solution.go

@@ -1,5 +1,77 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(grid [][]int) int {
+	group := 1
+	groupMapCount := map[int]int{}
+	rows, cols := len(grid), len(grid[0])
+	groupGrid := make([][]int, rows)
+	for i := range rows {
+		groupGrid[i] = make([]int, cols)
+	}
+
+	var (
+		bfs  func(int, int) int
+		dirs = [][2]int{
+			{0, 1}, {1, 0}, {0, -1}, {-1, 0},
+		}
+	)
+
+	bfs = func(x, y int) int {
+		q := [][2]int{{x, y}}
+		cnt := 0
+		groupGrid[x][y] = group
+		for len(q) > 0 {
+			cnt += len(q)
+			nq := make([][2]int, 0)
+			for _, cur := range q {
+				for _, d := range dirs {
+					nx, ny := cur[0]+d[0], cur[1]+d[1]
+					if nx < 0 || nx >= rows || ny < 0 || ny >= cols {
+						continue
+					}
+					if grid[nx][ny] == 1 && groupGrid[nx][ny] == 0 {
+						groupGrid[nx][ny] = group
+						nq = append(nq, [2]int{nx, ny})
+					}
+				}
+			}
+			q = nq
+		}
+		return cnt
+	}
+
+	ans := 0
+	for i := range rows {
+		for j := range cols {
+			if grid[i][j] == 1 && groupGrid[i][j] == 0 {
+				groupMapCount[group] = bfs(i, j)
+				ans = max(ans, groupMapCount[group])
+				group++
+			}
+		}
+	}
+
+	for i := range rows {
+		for j := range cols {
+			if grid[i][j] == 0 {
+				tmp := 1
+				used := map[int]struct{}{}
+				for _, d := range dirs {
+					nx, ny := i+d[0], j+d[1]
+					if nx < 0 || nx >= rows || ny < 0 || ny >= cols {
+						continue
+					}
+					if groupGrid[nx][ny] != 0 {
+						if _, ok := used[groupGrid[nx][ny]]; !ok {
+							tmp += groupMapCount[groupGrid[nx][ny]]
+							used[groupGrid[nx][ny]] = struct{}{}
+						}
+					}
+				}
+				ans = max(ans, tmp)
+			}
+		}
+	}
+
+	return ans
 }

leetcode/801-900/0827.Making-A-Large-Island/Solution_test.go

@@ -10,12 +10,12 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{{1, 0}, {0, 1}}, 3},
+		{"TestCase2", [][]int{{1, 1}, {1, 0}}, 4},
+		{"TestCase3", [][]int{{1, 1}, {1, 1}}, 4},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }