Runtime: 6 ms (Top 99.86%) | Memory: 10.30 MB (Top 99.86%)

Author: AnasImloul

scripts/algorithms/O/Open the Lock/Open the Lock.cpp

@@ -1,27 +1,33 @@
+// Runtime: 6 ms (Top 99.86%) | Memory: 10.30 MB (Top 99.86%)
+
 class Solution {
 public:
-    void setPermutations(const string& s, queue<pair<string, int>>& q, int count) {
-        for (int i=0; i<4; i++) {
-            int j = s[i]-'0';
-            char b = (10+j-1)%10 + '0', n = (10+j+1)%10 + '0';
-            auto tmp = s; tmp[i]=b;
-            q.push({tmp, count+1});
-            tmp = s; tmp[i]=n;
-            q.push({tmp, count+1});
-        }
-    }
     int openLock(vector<string>& deadends, string target) {
-        unordered_set<string> deadies(deadends.begin(), deadends.end());
-        queue<pair<string, int>> q({{"0000", 0}});
-        while (!q.empty()) {
-            auto t = q.front();
-            q.pop();
-            if (deadies.count(t.first))
-                continue;
-            if (t.first==target)
-                return t.second;
-            deadies.insert(t.first);
-            setPermutations(t.first, q, t.second);
+        if (target == "0000") return 0;
+        queue<int> queue;
+        queue.push(0);
+        bool seen[10000]{false};
+        for (auto& d : deadends)
+            seen[stoi(d)] = true;
+        int targ = stoi(target);
+        if (seen[0]) return -1;
+        for (int turns = 1; queue.size(); turns++) {
+            int qlen = queue.size();
+            for (int i = 0; i < qlen; i++) {
+                int curr = queue.front();
+                queue.pop();
+                for (int j = 1; j < 10000; j *= 10) {
+                    int mask = curr % (j * 10) / j,
+                        masked = curr - (mask * j);
+                    for (int k = 1; k < 10; k += 8) {
+                        int next = masked + (mask + k) % 10 * j;
+                        if (seen[next]) continue;
+                        if (next == targ) return turns;
+                        seen[next] = true;
+                        queue.push(next);
+                    }
+                }
+            }
         }
         return -1;
     }