首页 > 代码库 > Leetcode-Decode Ways
Leetcode-Decode Ways
A message containing letters from A-Z
is being encoded to numbers using the following mapping:
‘A‘ -> 1‘B‘ -> 2...‘Z‘ -> 26
Given an encoded message containing digits, determine the total number of ways to decode it.
For example,
Given encoded message "12"
,it could be decoded as "AB"
(1 2) or "L"
(12).
The number of ways decoding "12"
is 2.
Analysis:
This is a DP problem. d[i] is the number of ways to decode the first i chars.
d[i]=d[i-2]+d[i-1] if num(i-1,i) is a valid number and num(i,i) is a valid number.
NOTE: for a string with 2 chars, the number should be between 10 and 26. For a string with 1 char, the valid number should between 1 and 9. "0","01","02"...like this are all invalid.
Solution:
1 public class Solution { 2 public int numDecodings(String s) { 3 if (s.length()==0) return 0; 4 int[] d = new int[s.length()+1]; 5 d[0]=1; 6 for (int i=1;i<d.length;i++){ 7 d[i]=0; 8 int start = 0; 9 if (i-2>start) start = i-2;10 for (int k=start;k<i;k++){11 String temp = s.substring(k,i);12 if (temp.length()==1&&!temp.equals("0"))13 d[i]+=d[k];14 if (temp.length()==2){15 int num = Integer.parseInt(temp);16 if (num<=26 && num>=10)17 d[i]+=d[k];18 }19 }20 }21 return d[s.length()]; 22 }23 }
Leetcode-Decode Ways
声明:以上内容来自用户投稿及互联网公开渠道收集整理发布,本网站不拥有所有权,未作人工编辑处理,也不承担相关法律责任,若内容有误或涉及侵权可进行投诉: 投诉/举报 工作人员会在5个工作日内联系你,一经查实,本站将立刻删除涉嫌侵权内容。