
Given an equation, represented by words on the left side and the result on the right side.
You need to check if the equation is solvable under the following rules:
Each character is decoded as one digit (0 - 9).
No two characters can map to the same digit.
Each words[i] and result are decoded as one number without leading zeros.
Sum of numbers on the left side ( words ) will equal to the number on the right side ( result ).
Return true if the equation is solvable, otherwise return false .
2 <= words.length <= 51 <= words[i].length, result.length <= 7words[i], result contain only uppercase English letters.The number of different characters used in the expression is at most 10 .