Backward Digit Sums
FJ and his cows enjoy playing a mental game. They write down the numbers from 1 to N (1 <= N <= 10) in a certain order and then sum adjacent numbers to produce a new list with one fewer number. They repeat this until only >>继续阅读
与‘组合数学-计数’有关的日志
poj3421
15
10月
2015
X-factor Chains
Given a positive integer X, an X-factor chain of length m is a sequence of integers, 1 = X0, X1, X2, …, Xm = X satisfying Xi < Xi+1 and Xi | Xi+1 where a | b means a perfectly divides into b. Now we are interested in the maximum >>继续阅读
poj2992
15
9月
2015
Divisors
Your task in this problem is to determine the number of divisors of Cnk. Just for fun -- or do you need any special reason for such a useful computation?
Input
The input consists of several instances. Each instance consists of a single >>继续阅读
poj1496
15
9月
2015
Word Index
Encoding schemes are often used in situations requiring encryption or information storage/transmission economy. Here, we develop a simple encoding scheme that encodes particular types of words with five or fewer (lower case) letters as i >>继续阅读
lightoj1140
27
8月
2015
1140 - How Many Zeroes?
InputJimmy writes down the decimal representations of all natural numbers between and including m and n, (m ≤ n). How many zeroes will he write down?
Input starts with an integer T (≤ 11000), denoting the number of test ca >>继续阅读