91. Decode Ways (DP)

Java String to int
1.int a = Integer.parseInt(str);
2.int b = Integer.valueOf(str).intValue();

Char to int
int c1 = Character.getNumericValue(i);

考虑0的情况 0的前面是0的情况

 

 1 class Solution {
 2     public int numDecodings(String s) {
 3         int n = s.length();
 4         if(Character.getNumericValue(s.charAt(0)) == 0) return 0;
 5         if(n == 1) return 1;
 6         int[] res = new int[n + 1];
 7         res[0] = 1;
 8         res[1] = 1;
 9         for(int i = 1; i < n; i++) {
10             char c = s.charAt(i);
11             int c1 = Character.getNumericValue(c);
12             char b = s.charAt(i - 1);
13             int b1 = Character.getNumericValue(b);
14             if(c1 != 0) {
15                 if((b1 == 1) || (b1 == 2 &&  c1 <= 6)) {
16                     res[i + 1] = res[i - 1] + res[i];
17                 }else {
18                     res[i + 1] = res[i];
19                 }
20                 
21             }else {
22                 if(b1 <= 2 && b1 > 0) {
23                     res[i + 1] = res[i - 1];
24                 }else {
25                     return 0;
26                 }
27             }
28         }
29         return res[n];
30         
31         
32     }
33 }

 

posted @ 2018-08-16 09:21  jasoncool1  阅读(295)  评论(0)  编辑  收藏  举报