POJ 2891 Strange Way to Express Integers(中国剩余定理)

题目链接

虽然我不懂...

 #include <cstdio>
 #include <cstring>
 #include <map>
 #include <cmath>
 using namespace std;
 #define LL __int64
 LL p[],o[];
 LL x,y;
 LL ext_eulid(LL a,LL b)
 {
     LL t,d;
     if(b == )
     {
         x = ;
         y = ;
         return a;
     }
     d = ext_eulid(b,a%b);
     t = x;
     x = y;
     y = t - (a/b)*y;
     return d;
 }
 LL gcd(LL a,LL b)
 {
     return b == ?a:gcd(b,a%b);
 }
 int main()
 {
     int i,n,z;
     LL p1,o1,d,c,mod;
     while(scanf("%d",&n)!=EOF)
     {
         for(i = ;i < n;i ++)
         {
             scanf("%I64d%I64d",&p[i],&o[i]);
         }
         p1 = p[];
         o1 = o[];
         z = ;
         for(i = ;i < n&&z;i ++)
         {
             d = ext_eulid(p1,p[i]);
             c = o[i] - o1;
             if(c%d) z = ;
             mod = p[i]/d;
             x = ((c/d*x)%mod+mod)%mod;
             o1 = p1*x + o1;
             p1 = p1*mod;
         }
         if(!z)
         printf("-1\n");
         else
         printf("%I64d\n",o1);
     }
     return ;
 }