Create 9_numValidWords.cpp

11 November Leetcode Challenge 2021/9_numValidWords.cpp

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+class Solution {
+public:
+    vector<int> findNumOfValidWords(vector<string>& words, vector<string>& puzzles) {
+        int SIZE = 26;                                   // total character size
+        vector<vector<int>> trie = {vector<int>(SIZE)};  // we use vector to mimic the trie tree
+        vector<int> count = {0};                         // the number of words ending at node i
+        for (string word : words) {  // we do not use reference here to avoid modifying the input
+            sort(word.begin(), word.end());
+            word.erase(unique(word.begin(), word.end()), word.end());
+            if (word.size() <= 7) {  // longer words are never valid
+                // insert into trie
+                int node = 0;
+                for (char& letter : word) {
+                    int i = letter - 'a';
+                    if (trie[node][i] == 0) {  // push empty node
+                        trie.push_back(vector<int>(SIZE));
+                        count.push_back(0);
+                        trie[node][i] = trie.size() - 1;
+                    }
+                    node = trie[node][i];
+                }
+                count[node]++;
+            }
+        }
+        // search for valid words
+        function<int(int, bool, string&)> dfs = [&](int node, bool hasFirst, string& puzzle) {
+            int total = hasFirst ? count[node] : 0;
+            for (char& letter : puzzle) {
+                int i = letter - 'a';
+                if (trie[node][i]) {
+                    total += dfs(trie[node][i], hasFirst || (letter == puzzle[0]), puzzle);
+                }
+            }
+            return total;
+        };
+        vector<int> result;
+        for (string& puzzle : puzzles) {
+            result.push_back(dfs(0, false, puzzle));
+        }
+        return result;
+    }
+};