Leetcode 1088. Confusing Number II

Count how many integers in [1, N] consist only of digits {0,1,6,8,9} and whose 180° rotation (mapping 0→0,1→1,6↔9,8→8) produces a different valid number. The common approach is to generate candidates via DFS/backtracking (pruning by N) and check that the rotated value is not equal to the original.