[Leetcode] Decode Ways

Decode Ways

A message containing letters from was A-Z 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 " , it could be decoded as " AB "   (1 2) Or " L "   ().

The number of ways decoding is "12" 2.

Problem Solving Ideas:Dynamic Planning. This topic is discussed in two ways. D[i]+=d[i-2] If the last character is jointly encoded (and eligible) with the previous character. If the last character is encoded separately (and is eligible), then d[i] + = d[i-1]. Find their own dynamic planning is not familiar with the need to improve the analysis of the problem.

Class Solution {Public:int numdecodings (string s) {int len = s.length ();        if (len = = 0) {return 0;  } int* D = new Int[len + 1]; Indicates the first I character has d[i-1] in decoding mode d[0] = 1;        The 0-character case is known if (check (S[0])) {d[1] = 1 by analyzing 1, 2 characters;        }else{d[1] = 0;            } for (int i = 1; i < Len; i++) {d[i + 1] = 0;            if (check (S[i-1], s[i])) {d[i+1] + = d[i-1];            } if (check (S[i])) {d[i+1] + = D[i];        }} int result = D[len];        Delete[] D;    return result;        }private:bool Check (char c) {if (c = = ' 0 ') {return false;        }else{return true; }} bool Check (char C1, char C2) {if (c1 = = ' 0 ' | | C1 > ' 2 ' | | (c1== ' 2 ' && c2 > ' 6 '))        {return false;        }else{return true; }    }};

[Leetcode] Decode Ways