(Daily algorithm) LeetCode --- Decode Ways

(Daily algorithm) LeetCode --- Decode Ways

A message containing letters fromA-ZIs 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 cocould be decoded"AB"(1 2) or"L"(12 ).

The number of ways decoding"12"Is 2.

/* Determine whether the current character belongs to 1-9 each time (0 is definitely not good, because 0 is not in 1-26). If yes, the current character can be decode, in combination with f [n-1], f [n] + = f [n-1] then checks whether the string consisting of the current character and the previous character belongs to 10-26. If yes, then the two characters can be decode and combined with f [N-2], f [n] + = f [N-2] */class Solution {public: int numDecodings (string s) {int * a; a = new int [s. size () + 1]; memset (a, 0, (s. size () + 1) * sizeof (int); if (s. size () = 0) return 0; a [0] = 1; for (int I = 1; I <= s. size (); I ++) {if (s [I-1]! = '0') a [I] + = a [I-1]; if (I-2> = 0 & s [I-1]-'0' + 10 * (s [I-2]-'0 ') <= 26 & s [I-1]-'0' + 10 * (s [I-2]-'0')> = 10) a [I] + = a [I-2];} return a [s. size ()] ;}};