Create 0091-decode-ways.go

Memoization Accepted Submission: _https://leetcode.com/submissions/detail/872083022/_
Tabulation Accepted Submission: _https://leetcode.com/submissions/detail/872087433/_

Author: AP-Repositories

go/0091-decode-ways.go

@@ -0,0 +1,41 @@
+func numDecodingsMemoization(s string) int {
+    dp := make([]int, len(s) + 1)
+    dp[len(s)] = 1
+    
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if dp[i] != 0 {
+            return dp[i]
+        } else if s[i] == '0' {
+            return 0
+        }
+        
+        res := dfs(i + 1)
+        if i + 1 < len(s) && (
+            s[i] == '1' || s[i] == '2' && (s[i + 1] >= '0' && s[i + 1] <= '6')) {
+            res += dfs(i + 2)
+        }
+        dp[i] = res
+        return res
+    }
+    
+    return dfs(0)
+}
+
+func numDecodingsTabulation(s string) int {
+    dp := make([]int, len(s) + 1)
+    dp[len(s)] = 1
+    for i := len(s) - 1; i >= 0; i-- {
+        if s[i] == '0' {
+            dp[i] = 0
+        } else {
+            dp[i] = dp[i + 1]
+        }
+        
+        if i + 1 < len(s) && (
+            s[i] == '1' || s[i] == '2' && (s[i + 1] >= '0' && s[i + 1] <= '6')) {
+            dp[i] += dp[i + 2]
+        }
+    }
+    return dp[0]
+}