Leetcode 788. Rotated Digits
Count how many integers in [1, n] consist only of rotatable digits (0,1,8,2,5,6,9) and contain at least one digit that changes when rotated (2,5,6,9). This is a per-digit counting/digit-DP problem: treat each position independently and count numbers ≤ n that avoid invalid digits (3,4,7) while excluding those made only of self-mapping digits (0,1,8).
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Microsoft
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Late January, 2026
Microsoft
Mid-level
An integer x is a good if after rotating each digit individually by 180 degrees, we get a valid number that is different from x. Each digit must be rotated - we cannot choose to leave it alone.
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