3

Author: kedebug

DecodeWays/DecodeWays.cpp

@@ -0,0 +1,23 @@
+class Solution {
+public:
+    int numDecodings(string s) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        if (s.empty()) return 0;
+        
+        vector<int> dp(s.size() + 1, 0);
+        dp[0] = 1;
+        for (int i = 1; i <= s.size(); i++) {
+            if (s[i-1] != '0')
+                dp[i] = dp[i-1];
+            if (i > 1 && s[i-2] != '0') {
+                int x = s[i-2] - '0';
+                x = 10 * x + s[i-1] - '0';
+                if (0 < x && x <= 26) 
+                    dp[i] += dp[i-2];
+            }
+        }
+        return dp[s.size()];
+    }
+};