Kotlin: 91. Decode Ways

Author: MaratKhakim

kotlin/91-Decode-Ways.kt

@@ -0,0 +1,22 @@
+class Solution {
+    fun numDecodings(s: String): Int {
+        val n = s.length
+        val dp = IntArray(n+1)
+        dp[0] = 1
+        dp[1] = if (s[0] == '0') 0 else 1
+
+        for (i in 2..n) {
+            val curr = s[i-1] - '0'
+            val prev = s[i-2] - '0'
+            val num = 10*prev + curr
+
+            if (curr > 0)
+                dp[i] += dp[i-1]
+
+            if (num >= 10 && num <= 26)
+                dp[i] += dp[i-2]
+        }
+
+        return dp[n]
+    }
+}