Add Q212

Author: theFool32

212_WordSearch2/WordSearch2.cc

@@ -0,0 +1,104 @@
+struct Node {
+    Node(char ch):character(ch) { }
+    char character;
+    vector<Node*> next;
+};
+
+const char endChar = 1;
+class Trie {
+public:
+    /** Initialize your data structure here. */
+    Trie() {
+        head = new Node(endChar);
+    }
+
+    ~Trie() {
+        del(head);
+    }
+    
+    /** Inserts a word into the trie. */
+    void insert(string word) {
+        word += endChar;
+        Node *p = head;
+        for (auto&& ch : word) {
+            int index=0;
+            for (;index < p->next.size();++index) {
+                if (p->next[index]->character == ch) break;
+            }
+            if (index != p->next.size()) {
+                p = p->next[index];
+            } else {
+                p->next.push_back(new Node(ch));
+                p = p->next[p->next.size()-1];
+            }
+        }
+    }
+    
+    Node* getNext(char c, Node *p) {
+        int index=0;
+        for (;index < p->next.size();++index) {
+            if (p->next[index]->character == c) return p->next[index];
+        }
+        return nullptr;
+    }
+
+    inline Node* getHead() {
+        return head;
+    }
+
+private:
+    Node *head;
+
+    void del(Node *h) {
+        for (auto&& p : h->next) {
+            del(p);
+        }
+        delete h;
+    }
+};
+
+
+class Solution {
+public:
+    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
+        trie = new Trie();
+        for (auto&& word : words) {
+            trie->insert(word);
+        }
+        set<string> ans;
+        Node *head = trie->getHead();
+        for (int x = 0; x < board.size(); ++x) {
+            for (int y = 0; y < board[0].size(); ++y) {
+                _findWords(board, x, y, head, "", ans);
+            }
+        }
+        vector<string> actual_ans;
+        for (auto&& a : ans) {
+            actual_ans.push_back(a);
+        }
+        return actual_ans;
+    }
+
+private:
+    Trie *trie;
+    void _findWords(vector<vector<char>> &board, int x, int y, Node* p, string word, set<string> &ans) {
+        if (x < 0 || x >= board.size() || y < 0 || y >= board[0].size() || board[x][y] == 0) {
+            return;
+        }
+
+        if ((p=trie->getNext(board[x][y], p))) {
+            word += board[x][y];
+            if (trie->getNext(endChar, p)) {
+                ans.insert(word);
+            }
+
+            char c = board[x][y];
+            board[x][y] = 0;
+            _findWords(board, x+1, y, p, word, ans);
+            _findWords(board, x-1, y, p, word, ans);
+            _findWords(board, x, y-1, p, word, ans);
+            _findWords(board, x, y+1, p, word, ans);
+            board[x][y] = c;
+        }
+    }
+};