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[LeetCode] Decode Ways

时间:2015-03-30 20:29:37      阅读:111      评论:0      收藏:0      [点我收藏+]

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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.

 

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 Dynamic Programming String
 
思路1:递归,也就是dfs,功能正确,但大数据时超时
class Solution {
    int m_cnt;
    public:
        void numDecode(int dep, string s)
        {   
            if(dep == s.size())
            {   
                m_cnt ++; 
                return;
            }   

            numDecode(dep+1, s); 

            if((dep+1) < s.size())
            {   
                if( (s[dep] == 1 || s[dep] == 2) &&
                (s[dep+1] >= 0 && s[dep+1] <= 6) )
                    numDecode(dep+2, s); 
            }   
        }   
        int numDecodings(string s) {
            m_cnt = 0;
            numDecode(0, s); 
            return m_cnt;
        }   
};

思路二:动态规划

 

[LeetCode] Decode Ways

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原文地址:http://www.cnblogs.com/diegodu/p/4378723.html

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