BEST PYTHON SOLUTION WITH 50MS OF RUNTIME !
\n# Code\n\nclass Solution:\n    def minDeletionSize(self, strs: List[str]) -> int:\n        m, n = len(strs), len(strs[0])\n        res = 0\n        unsorted =
\n# Code\n```\nclass Solution:\n    def minDeletionSize(self, strs: List[str]) -> int:\n        m, n = len(strs), len(strs[0])\n        res = 0\n        unsorted = set(range(m - 1))\n        for j in range(n):\n            if any(strs[i][j] > strs[i+1][j] for i in unsorted):\n                res += 1\n            else:\n                unsorted -= {i for i in unsorted if strs[i][j] < strs[i+1][j]}\n        return res\n```
['Python3']