Count Number of Ways to Place Houses LeetCode solution in C++

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class Solution {
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 public:
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  typedef long long ll;
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  ll mod = 1e9 + 7;
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  int countHousePlacements(int n) {
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    ll house = 1, space = 1;
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    ll total = house + space;
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    for (int i = 2; i <= n; i++) {
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      house = space;
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      space = total;
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      total = (house + space) % mod;
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    }
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    return (total * total) % mod;
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  }
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};