luogu P1495 曹冲养猪（中国剩余定理）

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<algorithm>
 6 using namespace std;
 7 const long long N=20;
 8 long long n,x,y,a[N],b[N],m,ans;
 9 long long exgcd(long long a,long long b,long long &x,long long &y){
10     if(b==0){
11         x=1;y=0;
12         return a;
13     }
14     long long tmp=exgcd(b,a%b,x,y);
15     long long z=x;
16     x=y;y=z-(a/b)*y;
17     return tmp;
18 }
19 int main(){
20     scanf("%lld",&n);
21     m=1;
22     for(long long i=1;i<=n;i++){
23         scanf("%lld%lld",&a[i],&b[i]); 
24         m*=a[i];
25     }
26     for(long long i=1;i<=n;i++){
27         x=y=0;
28         exgcd(a[i],m/a[i],x,y);
29         ans+=(m/a[i])*b[i]*y;
30     }
31     ans=(ans%m+m)%m;
32     printf("%lld",ans);
33     return 0;
34 }