/**

* res.js

* @authors Joe Jiang ([email protected])

* @date 2017-04-06 18:43:29

*

* 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.

*

* @param {string} s

* @return {number}

*/

let numDecodings = function(s) {

let len = s.length,

num = 0,

matrix = new Array(len);

if (len===0) return len;

for (let i=0; i<len; i++) {

matrix[i] = new Array(len);

if (s[i] !== '0') {

matrix[i][i] = 1;

} else {

matrix[i][i] = 0;

}

}

let i=0;

for (let j=1; j<len; j++) {

let subOne = 0,

subTwo = 0,

subTwoStr = Number.parseInt(s.substring(j-1, j+1));

if (s[j] !== '0') {

subOne = matrix[i][j-1];

}

if (subTwoStr > 9 && subTwoStr < 27) {

subTwo = j-i === 1? 1:matrix[i][j-2];

}

if (subOne === 0 && subTwo === 0) return 0;

matrix[i][j] = subOne + subTwo;

console.log(matrix[i][j]);

}

return matrix[0][len-1];

};