这个题告诉我，一定要冷静，莫莫伤心流泪啊。#include<iostream> #include<cstring> using namespace std; char a[10000005]; int main() { long long cnt,ans,i,cas=1,len,cnt1; while(scanf("%s",a)!=EOF) { printf("Case #%d: ",cas++); len=strlen(a); for(i=len-1;a[i]=='0';i--); for(i=i-4,ans=0,cnt=cnt1=1;i>=0;i-=5) { ans=(ans+(((a[i]-'0')*10000+(a[i+1]-'0')*1000+(a[i+2]-'0')*100+(a[i+3]-'0')*10+a[i+4]-'0')%10001)*cnt%10001)%10001; cnt=cnt*100000%10001; } for(i+=4;i>=0;i--) { ans=(ans+(a[i]-'0')*cnt%10001)%10001; cnt=cnt*10%10001; } if(ans) printf("NO\n"); else printf("YES\n"); } return 0; }