diagonal.py

class Solution:
    # @param a : list of list of integers
    # @return a list of list of integers
    def diagonal(self, a):
        m = len(A)
        n = len(A[0])
        res = [0]*(m+n-1)
        
        res = self.build(res)
        res = self.fill(A,res,m,n)
        
        return res
        
    def build(self,res):
        for i in range(len(res)):
            res[i] = []
            
        return res
        
    def fill(self, A, res, m, n):
        for i in range(m):
            for j in range(n):
                res[i+j].append(A[i][j])
                
        return res