Create 1997.First-Day-Where-You-Have-Been-in-All-the-Rooms.cpp

Others/1997.First-Day-Where-You-Have-Been-in-All-the-Rooms/1997.First-Day-Where-You-Have-Been-in-All-the-Rooms.cpp

@@ -0,0 +1,22 @@
+class Solution {
+    long dp[100000];    
+    long M = 1e9+7;
+    int n;
+public:
+    int firstDayBeenInAllRooms(vector<int>& nextVisit) 
+    {
+        n = nextVisit.size();
+        dp[0] = 0;
+        dp[1] = 2;
+        long ret = 2;
+        for (int i=1; i<n-1; i++)
+        {
+            int prev = nextVisit[i];            
+            dp[i+1] = dp[i] + (dp[i]-dp[prev] + M +1) % M + 1;            
+            dp[i+1] %= M;
+        }
+        return dp[n-1];        
+    }
+
+
+};