Swift Solution with Brief Explanation.
Approach\n1. Create a 2D array of size n x n\n2. Initialize the array with 0\n3. Iterate over the array and fill the array with the LCP values\n4. Create a new 
# Approach\n1. Create a 2D array of size n x n\n2. Initialize the array with 0\n3. Iterate over the array and fill the array with the LCP values\n4. Create a new array of size n\n5. Initialize the array with "a"\n6. Iterate over the array and fill the array with the values from the LCP array\n7. If the value is 0, then increment the value of the previous element by 1\n8. If the value is greater than 26, then return an empty string\n9. Create a new 2D array of size n x n\n10. Initialize the array with 0\n11. Iterate over the array and fill the array with the LCP values\n12. Iterate over the array and check if the LCP values are same as the values in the new array\n13. If the values are not same, then return an empty string\n14. Return the array joined with ""\n\n\n# Complexity\n- Time complexity: O(n<sup>2</sup>)\n\n- Space complexity: O(n<sup>2</sup>)\n\n# Code\n```\nclass Solution {\n    func findTheString(_ lcp: [[Int]]) -> String {\n        let n = lcp.count\n        var arr = Array(repeating: "a", count: n)\n        var test = "a"\n        var found = false\n        for i in 1..<n {\n            test = "a"\n            found = false\n            for j in 0..<i {\n                test = max(test, arr[j])\n                if lcp[i][j] != 0 {\n                    found = true\n                    arr[i] = arr[j]\n                    break\n                }    \n            }\n            if found {\n                continue\n            }\n            test = String(Character(UnicodeScalar(test.unicodeScalars.first!.value + 1)!))\n            arr[i] = test\n            if test > "z" {\n                return ""\n            }\n        }\n        var dp = Array(repeating: Array(repeating: 0, count: n + 1), count: n + 1)\n        var val = 0\n        for i in (0..<n).reversed() {\n            for j in (0..<n).reversed() {\n                if arr[i] != arr[j] {\n                    val = 0\n                } else {\n                    val = 1 + dp[i + 1][j + 1]\n                }\n                \n                dp[i][j] = val\n            }\n        }\n        for i in (0..<n).reversed() {\n            for j in (0..<n).reversed() {\n                if dp[i][j] != lcp[i][j] {\n                    return ""\n                }\n            }\n        }\n        return arr.joined()\n    }\n}\n```
['Swift']