Leetcode 247. Strobogrammatic Number II
Generate all length-n strobogrammatic numbers—strings that appear identical when rotated 180°—by constructing valid digit pairs (0-0,1-1,6-9,8-8,9-6). The core challenge is using recursion/backtracking to place pairs from the outside in while avoiding leading zeros for n>1 and handling the single middle digit when n is odd.
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Late September, 2025
Uber
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# rotationally_symmetrical of len 1 is [0, 1, 8] # rotationally_symmetrical of len 2 is [11, 88, 69, 96] # rotationally_symmetrical of len 3 is ['101', '111', '181', '609', '619', '689', '808', '818', '888', '906', '916', '986']
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