北大ACM(Question-1006)

 1 Memory: 248K        Time: 0MS
 2 Language: C++        Result: Accepted
 3
 4 #include <iostream>
 5 
 6 using namespace std;
 7 int getGCD(int a,int b)//Greatest Common Divisor
 8 {
 9     if(a<b){a+=b;b=a-b;a=a-b;}
10     if(b==1) return 1;
11     else if(a%b==0) return a/b;
12     else return getGCD(b,a%b);
13 }
14 int getLCM(int a,int b)//Lowest Common Multiple
15 {
16     return a*b/getGCD(a,b);
17 }
18 int getMod1(int a,int b)//get N. a*N mod b ==1
19 {
20     int N=0;
21     while(a*N%b!=1){N++;}
22     return a*N;
23 }
24 int main()
25 {
26     int p,e,i,d,cnt=1;
27     int pe=getMod1(getLCM(23,28),33);
28     int pi=getMod1(getLCM(23,33),28);
29     int ei=getMod1(getLCM(28,33),23);
30     while(true)
31     {
32         cin>>p>>e>>i>>d;
33         if(p==-1&&e==-1&&i==-1&&d==-1) return 0;
34         int m=(ei*p+pi*e+pe*i)%(23*28*33)-d;
35         if(m<=0) m+=23*28*33;
36         cout<<"Case "<<cnt++<<": the next triple peak occurs in "<<m<<" days."<<endl;
37     }
38 }