Create 3213.Construct-String-with-Minimum-Cost.cpp

DFS/3213.Construct-String-with-Minimum-Cost/3213.Construct-String-with-Minimum-Cost.cpp

@@ -0,0 +1,62 @@
+class TrieNode
+{
+    public:
+    TrieNode* next[26];
+    int cost;
+    TrieNode()
+    {
+        for (int i=0; i<26; i++)
+            next[i] = NULL;
+        cost = -1;
+    }        
+};
+
+class Solution {
+    TrieNode* root = new TrieNode();
+    vector<int>memo;
+public:
+    int minimumCost(string target, vector<string>& words, vector<int>& costs) 
+    {
+        memo = vector<int>(target.size(), -1);
+
+        for (int i=0; i<words.size(); i++)
+        {
+            TrieNode* node = root;
+            for (auto ch: words[i])
+            {
+                if (node->next[ch-'a']==NULL)
+                    node->next[ch-'a'] = new TrieNode();
+                node = node->next[ch-'a'];
+            }
+            if (node->cost==-1)
+                node->cost = costs[i];
+            else
+                node->cost = min(node->cost, costs[i]);
+        }
+
+        int ret = dfs(target, 0);        
+        if (ret == INT_MAX/2) return -1;
+        else return ret;
+    }
+
+    int dfs(string& target, int cur)
+    {
+        if (cur==target.size()) return 0;
+        if (memo[cur] != -1) return memo[cur];
+
+        int ans = INT_MAX/2;
+        TrieNode* node = root;
+        for (int i=cur; i<target.size(); i++)
+        {
+            if (node->next[target[i]-'a']==NULL)
+                break;
+            node = node->next[target[i]-'a'];
+            if (node->cost!=-1)
+                ans = min(ans, node->cost + dfs(target, i+1));
+        }
+
+        memo[cur] = ans;
+
+        return ans;
+    }
+};