一、背景 數學系畢業，排名40% 在校修過六科 演算法 資結 離散 線代 計組 OS

考題 NCKU_CS_Math112 1. Fix the second digital : $1X1\text{~}~9X9$ Sum : $\frac{9(101+909)}{2}=4545$ Since $X$ from 0 to 9, the sum of this part is 45450 Fix the first and third digital : $X0X\text{~}X9X$ Sum : $\frac{9(10+90)}{2}=450$ Since $X$ from 1 to 9, this part is 4050