Recursion: Number of all n digit distinct integers using two integers a and b

Is my approach wrong? If not, then what is the mistake i am doing?
Code: https://ide.codingblocks.com/s/610516

Hi @anuragdeol2017
I dont understand what logic u are trying to apply… u can refer to my code https://ide.codingblocks.com/s/610599
try to dry run it… u would get better insight…

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