Could anybody explain testcase #4 without giving any hints? Testcase #4 is where the input is 15 and the expected result is 7.
In testcase #4 input is 15 so suppose our 1st rainbow no is 123456777654321. We see here total three 7 exists. so we can make 7 rainbow no by changing all nos. like
123456676654321
123455676554321
123445676544321
123345676543321
122345676543221
112345676543211
total six and 1st no was 123456777654321 means total 7 nos.
so output is 7.
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