91. Decode Ways (java)

Author: bluesword12350

solution/0091.Decode Ways/Solution.java

@@ -0,0 +1,19 @@
+class Solution {
+    public int numDecodings(String s) {
+        int len = s.length();
+        if (len == 0) return 0;
+        int current = s.charAt(0) == '0' ? 0 : 1;
+        int last = 1;
+        for (int i = 1; i < len; i++) {
+            int tmp = current;
+            if(s.charAt(i) == '0'){
+                if(s.charAt(i-1) == '1' || s.charAt(i-1) == '2') current = last;
+                else return 0;
+            }else if(s.charAt(i-1) == '1' || s.charAt(i-1) == '2' && s.charAt(i) <= '6') {
+                current += last;
+            }
+            last = tmp;
+        }
+        return current;
+    }
+}