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@@ -0,0 +1,29 @@
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+const MOD int = 1000000007
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+
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+func checkRecord(n int) int {
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+ // A, L, P
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+ var dp = [2][3]int{{1, 1, 0}, {1, 0, 0}}
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+ for i := 1; i < n; i++ {
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+ var nxt [2][3]int
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+ for A := 0; A <= 1; A++ {
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+ for L := 0; L <= 2; L++ {
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+ nxt[A][0] += dp[A][L] // Append P
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+ if L > 0 {
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+ nxt[A][L] += dp[A][L-1] // Append L
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+ }
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+ if A > 0 {
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+ nxt[A][0] += dp[A-1][L] // Append A
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+ }
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+ nxt[A][L] %= MOD
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+ }
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+ }
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+ dp = nxt
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+ }
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+ sum := 0
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+ for i := range dp {
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+ for _, v := range dp[i] {
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+ sum = (sum + v) % MOD
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+ }
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+ }
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+ return sum
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+}
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