Merge pull request #1853 from AP-Repositories/patch-1

Create 0212-word-search-ii.go

Author: AP-Repositories

go/0212-word-search-ii.go

@@ -0,0 +1,82 @@
+type TrieNode struct {
+    children map[byte]*TrieNode
+    isWord bool
+    refs int
+}
+
+func (this *TrieNode) addWord(word string) {
+    cur := this
+    cur.refs += 1
+    for c := 0; c < len(word); c++ {
+        if _, ok := cur.children[word[c]]; !ok {
+            cur.children[word[c]] = &TrieNode{children: make(map[byte]*TrieNode)}
+        }
+        cur = cur.children[word[c]]
+        cur.refs += 1
+    }
+    cur.isWord = true
+}
+
+func (this *TrieNode) removeWord(word string) {
+    cur := this
+    cur.refs += 1
+    for c := 0; c < len(word); c++ {
+        if _, ok := cur.children[word[c]]; ok {
+            cur = cur.children[word[c]];
+            cur.refs -= 1
+        }
+    }
+}
+
+func findWords(board [][]byte, words []string) []string {
+    root := &TrieNode{children: make(map[byte]*TrieNode)}
+    for _, w := range words {
+        root.addWord(w);
+    }
+    
+    ROWS, COLS := len(board), len(board[0])
+    res := make(map[string]bool)
+    visit := make(map[int]bool)
+    
+    var dfs func(int, int, *TrieNode, string)
+    dfs = func(r, c int, node *TrieNode, word string) {
+        if
+            r < 0 || r >= ROWS ||
+            c < 0 || c >= COLS ||
+            node.children[board[r][c]] == nil ||
+            node.children[board[r][c]].refs < 1 ||
+            visit[r*COLS + c] {
+            return
+        }
+        
+        visit[r*COLS + c] = true
+        node = node.children[board[r][c]]
+        word += string(board[r][c])
+        if node.isWord {
+            node.isWord = false
+            res[word] = true
+            root.removeWord(word)
+        }
+        
+        dfs(r + 1, c, node, word)
+        dfs(r - 1, c, node, word)
+        dfs(r, c + 1, node, word)
+        dfs(r, c - 1, node, word)
+        visit[r*COLS + c] = false
+    }
+    
+    for r := 0; r < ROWS; r++ {
+        for c := 0; c < COLS; c++ {
+            dfs(r, c, root, "")
+        }
+    }
+    return list(res)
+}
+
+func list(mapping map[string]bool) []string {
+    res := make([]string, 0, len(mapping))
+    for key, _ := range mapping {
+        res = append(res, key)
+    }
+    return res
+}