-
Notifications
You must be signed in to change notification settings - Fork 0
/
decodeWays.java
39 lines (32 loc) · 1.08 KB
/
decodeWays.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
/*
A message containing letters from A-Z is being encoded to numbers using the following mapping:
'A' -> 1
'B' -> 2
...
'Z' -> 26
Given a non-empty string containing only digits, determine the total number of ways to decode it.
Example 1:
Input: "12"
Output: 2
Explanation: It could be decoded as "AB" (1 2) or "L" (12).
Example 2:
Input: "226"
Output: 3
Explanation: It could be decoded as "BZ" (2 26), "VF" (22 6), or "BBF" (2 2 6).
*/
class Solution {
public int numDecodings(String s) {
if (s == null || s.lengthf() == 0) return 0;
int n = s.length();
int [] dp = new int [n+1]; //dp[i]: The number of the ways for i length string (i=1..n)
dp[0] = 1;
dp[1] = s.charAt(0) == '0' ? 0 : 1;
for(int i = 0; i <= n; i++){ //i is the length,not index
if(s.charAt(0) != '0') // 0 doesn't count
dp[i] = dp[i-1];
int twoDigits = Integer.valueOf(s.substring(i-2, i)); // 2 digits
if(twoDigits >= 10 && twoDigits <= 26)
dp[i] += dp[i-2]; //Adding all ways
}
}
}