two multidimensional array handling in ruby

I've got an array like this

[["1"], ["2","3"]]

In the beginning I had this algorithm

maxarray = []
i = 0
m = array.count
while i < m do
  x = 0
  s = array[i].count
  while x < s do
    maxarray[i][x] = (Integer(array[i][x]) + [Integer(maxarray[i-1][x-1]), Integer(maxarray[i-1][x])].max)
    开发者_高级运维x+=1 
  end
  i+=1
end

the error was this:

`<main>': undefined method `[]' for nil:NilClass (NoMethodError)

so I thought maybe the array indexes goes wrong so I extended my algorithm

maxarray = []
i = 0
m = array.count
while i < m do
  x = 0
  s = array[i].count
  while x < s do
    if i-1 < 0 
        item2 = 0
    elsif i-1 < 0 && x-1 < 0 
        item1 = 0
    else item1 = maxarray[i-1][x-1] 
         item2 = maxarray[i-1][x] 
    end
    maxarray[i][x] = (Integer(array[i][x]) + [Integer(item1), Integer(item2)].max)
    x+=1 
  end
  i+=1
end

but now i have an different error:

`Integer': can't convert nil into Integer (TypeError)

how can prevent this error and run the script?

---

Why you don't flatten the array and make your computing? Certainly it will make your function simplier.