400. Nth Digit

Find the n th digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...

Note: n is positive and will fit within the range of a 32-bit signed integer ( n < 231).

Example 1:

Input:
3

Output:
3

Example 2:

Input:
11

Output:
0

Explanation:
The 11th digit of the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ... is a 0, which is part of the number 10.

# @lc code=start
using LeetCode

function find_nth_digit(n::Int)
    ant = [0, 10, 190, 2890, 38890, 488890, 5888890, 68888890, 788888890]
    num_begin = [0, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000]
    idx = searchsortedlast(ant, n)
    num = (n - ant[idx]) ÷ idx + num_begin[idx]
    posi = (n - ant[idx]) % idx
    return num % (10^(idx - posi)) ÷ 10^(idx - posi - 1)
end
# @lc code=end

find_nth_digit (generic function with 1 method)

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