Given an array of positive integers a, your task is to calculate the sum of every possible a[i] ∘a[j], where a[i]∘a[j] is the concatenation of the string representations of a[i] and a[j] respectively.
Example
For a = [10, 2], the output should be concatenationsSum(a) = 1344.
a[0] ∘a[0] = 10 ∘10 = 1010,
a[0] ∘a[1] = 10 ∘2 = 102,
a[1] ∘a[0] = 2 ∘10 = 210,
a[1] ∘a[1] = 2 ∘2 = 22.
So the sum is equal to 1010 + 102 + 210 + 22 = 1344.
For a = [8], the output should be concatenationsSum(a) = 88.
There is only one number in a, and a[0] ∘a[0] = 8 ∘8 = 88, so the answer is 88.
Input/Output
[execution time limit] 3 seconds (java)
[input] array.integer a
A non-empty array of positive integers.
Guaranteed constraints:
1 ≤ a.length ≤ 105,
1 ≤ a[i] ≤ 106.
[output] integer64
The sum of all a[i] ∘a[j]s. It's guaranteed that the answer is less than 253.
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