JavaScript | Two pointer | O(n)
Approach\n Describe your approach to solving the problem. \nTwo pointer\n\n# Complexity\n- Time complexity: O(n)\n Add your time complexity here, e.g. O(n) \n\n
# Approach\n<!-- Describe your approach to solving the problem. -->\nTwo pointer\n\n# Complexity\n- Time complexity: O(n)\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity: O(1)\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code - I\n```\n/**\n * @param {number[]} nums\n * @return {number}\n */\nvar findTheArrayConcVal = function(nums) {\n    let i = 0, j = nums.length-1, sum = 0;\n    while(i<j) {\n        sum += Number(nums[i]+\'\'+nums[j]);\n        i++;\n        j--;\n    }\n    if(i===j) sum += nums[i];\n    return sum;\n};\n```\n# Code - II\n```\n/**\n * @param {number[]} nums\n * @return {number}\n */\nvar findTheArrayConcVal = function(nums) {\n    let i = 0, j = nums.length-1, sum = 0;\n    while(i<=j) {\n        sum += Number(i===j ? nums[i] : `${nums[i]}`+`${nums[j]}`);\n        i++; j--;\n    }\n    return sum;\n};\n```
['Two Pointers', 'JavaScript']