代码改变世界

leetcode - Decode Ways

2013-03-28 12:12  张汉生  阅读(214)  评论(0)  编辑  收藏  举报

题目描述：点击此处

 1 class Solution {
 2 public:
 3   int numDecodings(string s) {
 4     // Start typing your C/C++ solution below
 5     // DO NOT write int main() function
 6     int len = s.length();
 7     if (len ==0 || (len>=1&&s.at(0)=='0'))
 8       return 0;
 9     else if (len==1)
10       return 1;
11     int lastTwo = 1; int lastOne = 1;
12     int cur;
13     for (int i=1; i<len; i++){
14       cur = 0;
15       if (s.at(i)!='0')
16         cur = lastOne;
17       if (s.at(i-1)=='1' || (s.at(i-1)=='2'&&s.at(i)<='6'))
18         cur += lastTwo;
19       lastTwo = lastOne;
20       lastOne = cur;
21     }
22     return cur;
23   }
24 };