Create 2976. Minimum Cost to Convert String I (#539)

Author: Chayandas07

2976. Minimum Cost to Convert String I

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+class Solution {
+     unordered_map<char, unordered_map<char, long long>> memo;
+private:
+    long long dijkstra(char src, char tar, unordered_map<char, vector<pair<char, long long>>> &mp)
+    {
+         if (memo[src].find(tar) != memo[src].end()) return memo[src][tar];
+        
+        priority_queue<pair<long long, char>, vector<pair<long long, char>>, greater<pair<long long, char>>> pq;
+        unordered_map<char, long long>distance;
+        
+        pq.push({0, src});
+        distance[src] = 1;
+        
+        while(!pq.empty())
+        {
+            long long topCost = pq.top().first;
+            char topChar = pq.top().second;
+            pq.pop();
+            
+            if (topChar == tar) 
+            {
+                memo[src][tar] = topCost;
+                return topCost;
+            }
+            
+            for (auto x:mp[topChar])
+            {
+                char mpChar = x.first;
+                long long mpCost = x.second;
+                
+                if (distance.find(mpChar) == distance.end() or topCost + mpCost < distance[mpChar])
+                {
+                    distance[mpChar] = topCost + mpCost;
+                    pq.push({distance[mpChar], mpChar});
+                }
+            }
+            
+        }
+        
+        memo[src][tar] = 0;
+        return -1;
+    }
+    
+public:
+    long long minimumCost(string source, string target, vector<char>& original, vector<char>& changed, vector<int>& cost) 
+    {
+        unordered_map<char, vector<pair<char, long long>>>mp;
+        for (int i = 0; i < original.size(); ++i)
+        {
+            mp[original[i]].push_back({changed[i], cost[i]});
+        }
+        
+        long long ans = 0;
+        for (int i = 0; i < source.size(); ++i)
+        {
+            if (source[i] != target[i]) 
+            {
+                long long Cost = dijkstra(source[i], target[i], mp);
+                if (Cost == -1)      return -1;
+                ans += Cost;
+            }
+        }
+        
+        return ans; 
+    }
+};