Easy Solution in java| O(N) time
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:O(N)\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\nclass Solution {\n    public long findTheArrayConcVal(int[] nums) {\n        int j = nums.length-1;\n        ArrayList<Integer> k = new ArrayList<>();\n        if (nums.length%2==0) {\n            for (int i = 0; i < nums.length / 2; i++) {\n\n                String n = Integer.toString(nums[i]);\n                String m = Integer.toString(nums[j]);\n                j--;\n                k.add(Integer.valueOf(n + m));\n            }\n        }\n        else{\n            for (int i = 0; i < nums.length / 2; i++) {\n\n                String n = Integer.toString(nums[i]);\n                String m = Integer.toString(nums[j]);\n                j--;\n                k.add(Integer.valueOf(n + m));\n            }\n            k.add(nums[nums.length/2]);\n        }\n        long sum = 0;\n        for (int i = 0; i < k.size(); i++) {\n            sum+=k.get(i);\n        }\n\n        return sum;\n    }\n}\n```
['Java']