func solution(_ arr1:[[Int]], _ arr2:[[Int]]) -> [[Int]] {
var result = [[Int]]()
for i in 0..<arr1.count {
var num = [Int]()
for j in 0..<arr1[i].count {
var sum = Int(arr1[i][j]) + Int(arr2[i][j])
num.append(sum)
}
result.append(num)
}
return result
}
solution([[1,2],[2,3]], [[3,4],[5,6]])
solution([[1],[2]], [[3],[4]])