Tag Archives: SGU118

SGU 118 解题报告


118. Digital Root

time limit per test: 0.50 sec.
memory limit per test: 4096 KB

Let f(n) be a sum of digits for positive integer n. If f(n) is one-digit number then it is a digital root for n and otherwise digital root of n is equal to digital root of f(n). For example, digital root of 987 is 6. Your task is to find digital root for expression A1*A2*…*AN + A1*A2*…*AN-1 + … + A1*A2 + A1.

设 f(n) 表示十进制正整数 n 的各位数字之和。如果 f(n) 是一个1位数那么他就是 n 的数根。否则的话 f(n) 的数根就是 n 的数根。举例说明:987的数根是 6(9+8+7=24 2+4=6)。你的任务是算出这样的数的数根: A1*A2*…*AN + A1*A2*…*AN-1 + … + A1*A2 + A1。


Input file consists of few test cases. There is K (1 <=K <= 5) in the first line of input. Each test case is a line. Positive integer number N is written on the first place of test case (N<=1000). After it there are N positive integer numbers (sequence A). Each of this numbers is non-negative and not more than 109.

输入包含K个测试点.在第一行会给出 K (1 <= K <= 5).每个测试点一行.首先是一个正整数N (N <= 1000). 接着N个非负整数 (序列 A). 均不超过109.


Write one line for every test case. On each line write digital root for given expression.