1d dp
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\nclass Solution {\npublic:\n    int firstDayBeenInAllRooms(vector<int>& nv) {\n        int n = nv.size(), mod = 1e9 + 7, i = 0, ans = 0;\n        vector<int> dp(n, 0);\n        while (i < n - 1) {\n            dp[i] = ans;\n            ans = (ans + 1) % mod;\n            i = (i + 1) % n;\n            ans = (ans + ((ans) - (dp[nv[i - 1]]) + mod) % mod) % mod;\n        }\n        return ans;\n    }\n};\n```
['C++']