Python 3   ||   5 lines,  iteration   ||   T/S: 86% / 72%
\nclass Solution:\n    def findTheArrayConcVal(self, nums: List[int]) -> int:\n\n        n=len(nums)\n\n        ans=nums[n//2] if n%2 else 0\n\n        for i in
```\nclass Solution:\n    def findTheArrayConcVal(self, nums: List[int]) -> int:\n\n        n=len(nums)\n\n        ans=nums[n//2] if n%2 else 0\n\n        for i in range(n//2): \n            ans += int(str(nums[i])+str(nums[-i-1]))\n        \n        return ans\n```\n[https://leetcode.com/problems/find-the-array-concatenation-value/submissions/1295835207/](https://leetcode.com/problems/find-the-array-concatenation-value/submissions/1295835207/)\n\nI could be wrong, but I think that time complexity is *O*(*N*) and space complexity is *O*(1), in which *N* ~ `len(nums)`.\n
['Python3']