514- Freedom Trail

Author: bhavishy2801

514. Freedom Trail.cpp

@@ -0,0 +1,32 @@
+class Solution {
+public:
+    int n;
+    string ring,key;
+    vector<vector<int>> memo;
+    array<vector<int>,26> pos;
+
+    int dfs(int cur,int kidx) {
+        if (kidx==(int)key.size()) return 0;
+        int &res=memo[cur][kidx];
+        if (res != -1) return res;
+        res=INT_MAX/4;
+        int ch=key[kidx]-'a';
+        for (int p : pos[ch]) {
+            int diff=abs(cur-p);
+            int dist=min(diff,n-diff);
+            int sub=dfs(p,kidx+1);
+            res=min(res,dist+1+sub);
+        }
+        return res;
+    }
+
+    int findRotateSteps(string ring_,string key_) {
+        ring=ring_;
+        key=key_;
+        n=ring.size();
+        memo.assign(n,vector<int>(key.size(),-1));
+        for (int i=0; i<26; ++i) pos[i].clear();
+        for (int i=0; i<n; ++i) pos[ring[i]-'a'].push_back(i);
+        return dfs(0,0);
+    }
+};