Create 1639. Number of Ways to Form a Target String Given a Dictionary

1639. Number of Ways to Form a Target String Given a Dictionary

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+class Solution {
+ public: 
+  int numWays(vector<string>& words, string target) {
+    constexpr int kMod = 1'000'000'007;
+    const int wordLength = words[0].length();
+    vector<long> dp(target.size() + 1);
+    dp[0] = 1;
+    for (int j = 0; j < wordLength; ++j) {
+      vector<int> count(26);
+      for (const string& word : words)
+        ++count[word[j] - 'a'];
+      for (int i = target.size(); i > 0; --i) {
+        dp[i] += dp[i - 1] * count[target[i - 1] - 'a'];
+        dp[i] %= kMod;
+      }
+    }
+    return dp[target.length()];
+  };
+};