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@@ -0,0 +1,46 @@
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+const MOD int = 1000000007
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+
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+func numDecodings(s string) int {
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+ n := len(s)
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+ if n == 0 {
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+ return 1
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+ }
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+ dp := make([]int, n+1)
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+ dp[0] = 1
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+ switch s[0] {
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+ case '*':
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+ dp[1] = 9
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+ case '0':
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+ return 0
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+ default:
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+ dp[1] = 1
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+ }
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+ for i := 2; i <= n; i++ {
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+ if s[i-1] == '*' {
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+ dp[i] = 9 * dp[i-1] // blabla | *
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+ if s[i-2] == '1' || s[i-2] == '*' {
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+ dp[i] += 9 * dp[i-2] // blabla | 1*
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+ }
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+ if s[i-2] == '2' || s[i-2] == '*' {
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+ dp[i] += 6 * dp[i-2] // blabla | 2*
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+ }
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+ } else if s[i-1] != '0' {
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+ dp[i] = dp[i-1]
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+ if s[i-2] == '1' || s[i-2] == '*' {
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+ dp[i] += dp[i-2] // blabla | 17
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+ }
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+ if s[i-1] < '7' && (s[i-2] == '2' || s[i-2] == '*') {
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+ dp[i] += dp[i-2] // blabla | 26
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+ }
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+ } else {
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+ if s[i-2] == '1' || s[i-2] == '*' {
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+ dp[i] += dp[i-2] // blabla | 10
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+ }
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+ if s[i-2] == '2' || s[i-2] == '*' {
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+ dp[i] += dp[i-2] // blabla | 20
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+ }
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+ }
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+ dp[i] %= MOD
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+ }
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+ return dp[n]
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+}
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