Javascript dp 171ms
\nconst initialize2DArray = (n, m) => [...Array(n)].map(() => Array(m).fill(0));\nconst char = (ascii) => String.fromCharCode(ascii);\n\nconst findTheString = (
```\nconst initialize2DArray = (n, m) => [...Array(n)].map(() => Array(m).fill(0));\nconst char = (ascii) => String.fromCharCode(ascii);\n\nconst findTheString = (g) => {\n    let n = g.length, res = Array(n).fill(-1), max = 1, dp = initialize2DArray(n, n);\n    res[0] = 0;\n    for (let i = 1; i < n; i++) {\n        let match = false;\n        for (let j = 0; j < i; j++) {\n            if (g[i][j] > 0) {\n                res[i] = res[j];\n                match = true;\n                break;\n            }\n        }\n        if (!match) {\n            res[i] = max;\n            if (res[i] >= 26) return \'\';\n            max++;\n        }\n    }\n    dp[n - 1][n - 1] = 1;\n    for (let i = n - 2; ~i; i--) {\n        for (let j = i; j < n; j++) {\n            if (res[i] != res[j]) {\n                dp[i][j] = 0;\n            } else {\n                dp[i][j] = j + 1 < n ? dp[i + 1][j + 1] + 1 : 1;\n            }\n        }\n    }\n    for (let i = 0; i < n; i++) {\n        for (let j = i; j < n; j++) {\n            if (dp[i][j] != g[i][j] || dp[i][j] != g[j][i]) return \'\';\n        }\n    }\n    return res.map(x => char(x + 97)).join("");\n};\n```
['Dynamic Programming', 'JavaScript']