Implement dominoes push simulation

838. Push Dominoes.cpp

@@ -0,0 +1,36 @@
+class Solution {
+public:
+    string pushDominoes(string dominoes) {
+        int n = dominoes.size();
+        vector<int> left(n, 0), right(n, 0);
+
+        // Step 1: Propagate rightward forces
+        int force = 0;
+        for (int i = 0; i < n; i++) {
+            if (dominoes[i] == 'R') force = n;          // reset strong rightward force
+            else if (dominoes[i] == 'L') force = 0;     // leftward push blocks rightward
+            else force = max(force - 1, 0);             // decrease over distance
+            right[i] = force;
+        }
+
+        // Step 2: Propagate leftward forces
+        force = 0;
+        for (int i = n - 1; i >= 0; i--) {
+            if (dominoes[i] == 'L') force = n;          // reset strong leftward force
+            else if (dominoes[i] == 'R') force = 0;     // rightward push blocks leftward
+            else force = max(force - 1, 0);             // decrease over distance
+            left[i] = force;
+        }
+
+        // Step 3: Determine final state
+        string result;
+        for (int i = 0; i < n; i++) {
+            if (left[i] == right[i]) result += '.';
+            else if (left[i] > right[i]) result += 'L';
+            else result += 'R';
+        }
+
+        return result;
+    }
+};
+