标签:style blog color io for div amp log
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.
就是要注意0的出现
class Solution { public: int numDecodings(string s) { int len = s.size(); if(len==0) return 0; vector<int> num(len,0);//第i个位置记录从s的第0个位置开始到第i个位置共有几种解码方式 if(len>=1 && s[0]==‘0‘) return 0; num[0] = 1; if(len==1) return num[0]; string s0 = s.substr(0,2); int d = sToInt(s0); int n=0; if(d>10 && d<=26 && d!=20) num[1] = 2; else if((s[1] ==‘0‘ && (s[0]==‘1‘|| s[0]==‘2‘))||s[1]!=‘0‘) num[1] = num[0]; else return 0; for(int i=2;i<len;i++){ if(s[i-1]==‘0‘){ if(s[i]!=‘0‘){ num[i] = num[i-1]; continue; } else return 0; } s0 = s.substr(i-1,2); d = sToInt(s0); if(s[i]==‘0‘){ if(d==10 || d==20){ num[i] = num[i-2]; continue; } else return 0; } if(d>10 && d<=26 ) num[i] = num[i-1]+num[i-2]; else num[i] = num[i-1]; }//end for return num[len-1]; } private: int sToInt(string s){ istringstream is(s); int d; is>>d; return d; } };
[LeetCode] Decode Ways(DP),布布扣,bubuko.com
标签:style blog color io for div amp log
原文地址:http://www.cnblogs.com/Xylophone/p/3909556.html