leetcode 91

leetcode/91/91.go

@@ -0,0 +1,15 @@
+func numDecodings(s string) int {
+    n := len(s)
+    f := make([]int, n+1)
+    f[0] = 1
+    for i := 1; i <= n; i++ {
+        if s[i-1] != '0' {
+            f[i] += f[i-1]
+        }
+        if i > 1 && s[i-2] != '0' && ((s[i-2]-'0')*10+(s[i-1]-'0') <= 26) {
+            f[i] += f[i-2]
+        }
+    }
+    return f[n]
+}
+