Repeated Digit Count - FAANG Problems

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Repeated Digit Count - FAANG Problems | Repovive

Hint

A uniform integer is one where every digit is the same, like $1$ , $22$ , $333$ , or $9999$ .

Notice that for each digit length $d$ , there are exactly $9$ uniform integers (one for each digit $1$ through $9$ ).

Key question: Instead of checking every integer in $[A, B]$ , can you enumerate only the uniform integers and count which ones fall in range?

A uniform integer is one where every digit is the same, like $1$ , $22$ , $333$ , or $9999$ .

Notice that for each digit length $d$ , there are exactly $9$ uniform integers (one for each digit $1$ through $9$ ).

Key question: Instead of checking every integer in $[A, B]$ , can you enumerate only the uniform integers and count which ones fall in range?