UVA 350 Pseudo-Random Numbers

 Pseudo-Random Numbers 

Computers normally cannot generate really random numbers, but frequently are used to generate sequences of pseudo-random numbers. These are generated by some algorithm, but appear for all practical purposes to be really random. Random numbers are used in many applications, including simulation.

A common pseudo-random number generation technique is called the linear congruential method. If the last pseudo-random number generated was L, then the next number is generated by evaluating (  , where Z is a constant multiplier, I is a constant increment, and M is a constant modulus. For example, suppose Z is 7, I is 5, and M is 12. If the first random number (usually called theseed) is 4, then we can determine the next few pseudo-random numbers are follows:

As you can see, the sequence of pseudo-random numbers generated by this technique repeats after six numbers. It should be clear that the longest sequence that can be generated using this technique is limited by the modulus, M.

In this problem you will be given sets of values for Z, I, M, and the seed, L. Each of these will have no more than four digits. For each such set of values you are to determine the length of the cycle of pseudo-random numbers that will be generated. But be careful: the cycle might not begin with the seed!

Input

Each input line will contain four integer values, in order, for Z, I, M, and L. The last line will contain four zeroes, and marks the end of the input data. L will be less than M.

Output

For each input line, display the case number (they are sequentially numbered, starting with 1) and the length of the sequence of pseudo-random numbers before the sequence is repeated.

Sample Input

7 5 12 45173 3849 3279 15119111 5309 6000 12341079 2136 9999 12370 0 0 0

Sample Output

Case 1: 6Case 2: 546Case 3: 500Case 4: 220

根据题目给的那个公式。求出形成的数字周期的周期长度

开一个vis数组标记已经用到过的数字。。每次标记的值都+1。直到遇到一个已经标记过的就结束。输出起始和结束时候标记值得差

#include <stdio.h>#include <string.h>int z, i, m, l;int ll;int star;int end;int vis[100005];void tra(){    l = (z * l + i) % m;}int main(){    int tt = 1;    while (scanf("%d%d%d%d", &z, &i, &m, &l) != EOF && z && i && m && l)    {memset(vis, 0, sizeof(vis));int ttt = 1;while (1){if (vis[l])break;vis[l] = ttt ++;end = l;    tra();}star = l;printf("Case %d: %d\n", tt ++ , vis[end] - vis[star] + 1);    }    return 0;}