Create 1997-first-day-where-you-have-been-in-all-the-rooms.js

Author: everthis

1997-first-day-where-you-have-been-in-all-the-rooms.js

@@ -0,0 +1,18 @@
+/**
+ * @param {number[]} nextVisit
+ * @return {number}
+ */
+const firstDayBeenInAllRooms = function(nextVisit) {
+        const P = 1e9+7;
+        const n = nextVisit.length;
+        const f = Array(n).fill(0) ;
+        f[0] = 0;
+
+        for (let i = 1; i < n; i++) {
+            f[i] = ((
+                    (2 * f[i - 1]) % P
+                            + P - f[nextVisit[i - 1]]) % P + 2) % P;
+        }
+
+        return f[n - 1];
+};