Count Number of Ways to Place Houses LeetCode solution in Java

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class Solution {
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  int mod = (int) 1e9 + 7;
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  public int countHousePlacements(int n) {
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    if (n == 1) return 4;
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    if (n == 2) return 9;
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    long a = 2;
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    long b = 3;
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    if (n == 1) return (int) (a % mod);
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    if (n == 2) return (int) (b % mod);
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    long c = 0;
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    for (int i = 3; i <= n; i++) {
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      c = (a + b) % mod;
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      a = b % mod;
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      b = c % mod;
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    }
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    return (int) ((c * c) % mod);
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  }
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}