Hi guy, I was trying to solve this problem (vietnameses) : https://codeforces.net/group/FLVn1Sc504/contest/274522/problem/Q
Translate : Given an integer n. Write all number from 1 to n and calculate sum of digit of all number.
For ex :
n = 5: 1 + 2 + 3 + 4 + 5 = 15
I found a solution for problem above : https://vnoi.info/problems/show_solution/SPSUM/1387592/
But i don't understand f10[] array in that code (after 5 hours thinking and still don't get it). Can somebody explain for me?