leetcode 91. 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 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).
dp solution
class Solution {
public:
int numDecodings(string s) {
if(s.length() == 0 || s == '0') return 0;
vector <int> dp(s.length()+1,0);
dp = 1;
dp = 1;
int max1 = 0;
for(int i = 2; i <= s.length(); i++){
if(s >= '1' && s < '27'){
dp += dp;
}
if(s == '1' || (s == '2' && s >= '0' && s <= '6')){
dp += dp;
}
}
return dp;
}
};
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