Add solution and test-cases for problem 212

Author: 0xff-dev

leetcode/201-300/0212.Word-Search-II/1.jpg

@@ -1,28 +1,27 @@
 # [212.Word Search II][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
+Given an `m x n` `board` of characters and a list of strings `words`, return all words on the board.
+
+Each word must be constructed from letters of sequentially **adjacent cells**, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.
+
+**Example 1:**  
 
-**Example 1:**
+![1](./1.jpg)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: board = [["o","a","a","n"],["e","t","a","e"],["i","h","k","r"],["i","f","l","v"]], words = ["oath","pea","eat","rain"]
+Output: ["eat","oath"]
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./2.jpg)
 
-### 思路1
-> ...
-Word Search II
-```go
 ```
-
+Input: board = [["a","b"],["c","d"]], words = ["abcb"]
+Output: []
+```
 
 ## 结语
 

leetcode/201-300/0212.Word-Search-II/2.jpg

@@ -1,5 +1,67 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+type trieNode212 struct {
+	child [26]*trieNode212
+	word  string
+}
+
+func buildTrieNode212(words []string) *trieNode212 {
+	root := &trieNode212{}
+	for _, word := range words {
+		walker := root
+		// a, b
+		for i, b := range word {
+			index := b - 'a'
+			if walker.child[index] == nil {
+				walker.child[index] = &trieNode212{}
+			}
+			walker = walker.child[index]
+			if i == len(word)-1 {
+				walker.word = word
+			}
+		}
+	}
+	return root
+}
+func Solution(board [][]byte, words []string) []string {
+	rows, cols := len(board), len(board[0])
+	tree := buildTrieNode212(words)
+	var (
+		search func(int, int, *trieNode212)
+		dirs   = [][]int{
+			{0, 1}, {0, -1}, {1, 0}, {-1, 0},
+		}
+	)
+	found := map[string]struct{}{}
+	search = func(x, y int, tree *trieNode212) {
+		if x < 0 || x >= rows || y < 0 || y >= cols || board[x][y] == '|' {
+			return
+		}
+		index := board[x][y] - 'a'
+		node := tree.child[index]
+		if node == nil {
+			return
+		}
+		if node.word != "" {
+			found[node.word] = struct{}{}
+		}
+		source := board[x][y]
+		board[x][y] = '|'
+		for _, dir := range dirs {
+			nx, ny := x+dir[0], y+dir[1]
+			walker := node
+			search(nx, ny, walker)
+		}
+		board[x][y] = source
+	}
+	for r := 0; r < rows; r++ {
+		for c := 0; c < cols; c++ {
+			search(r, c, tree)
+		}
+	}
+	var ret []string
+	for key := range found {
+		ret = append(ret, key)
+	}
+	return ret
 }

leetcode/201-300/0212.Word-Search-II/README.md

@@ -10,30 +10,37 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		board  [][]byte
+		words  []string
+		expect []string
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]byte{
+			{'o', 'a', 'a', 'n'},
+			{'e', 't', 'a', 'e'},
+			{'i', 'h', 'k', 'r'},
+			{'i', 'f', 'l', 'v'},
+		}, []string{"oath", "pea", "eat", "rain"}, []string{"oath", "eat"}},
+		{"TestCase2", [][]byte{
+			{'a', 'b'}, {'c', 'd'},
+		}, []string{"abcd"}, nil},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.board, c.words)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v",
+					c.expect, got, c.board, c.words)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }