First Day Where You Have Been in All the Rooms LeetCode solution in C++

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#define ll long long
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int mod = 1e9 + 7;
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class Solution {
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 public:
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  int firstDayBeenInAllRooms(vector<int> &nextVisit) {
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    int n = nextVisit.size();
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    vector<vector<ll>> dp(n, vector<ll>(2, 0));
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    dp[0][0] = 2;
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    dp[0][1] = 1;
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    for (int i = 1; i < n; i++) {
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      dp[i][1] = dp[i - 1][0] + 1;
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      if (i == n - 1) break;
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      dp[i][0] = (dp[i][1] + (dp[i - 1][0] - dp[nextVisit[i]][1]) + 2) % mod;
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    }
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    return (dp[n - 1][1] + mod - 1) % mod;
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  }
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};