题解 P1009 【阶乘之和】

博客已挂 ### 写python代码的，难道你们不知道联赛不支持python？ ### 写打表的,你们的generator在哪里？ python自带高精度，可是联赛中不支持 c++联赛中允许使用，但是得自己写高精度 这道题数据范围是 $n≤50$ 是否能用一种方法，集聚两家的智慧 当然有 ## 打表 ### 具体思路 先用python打表，然后以字符串形式存入c++代码中 ### 实现 python代码 ```python f=open(r'point.txt','w') #存入文件 sum=1 i=2 last=1 n=int(input()) while i<=n: last*=i sum+=last i+=1 #主函数 f.write('"') #上引号 f.write(str(sum)) #具体值 f.write('",') #下引号与逗号 f.close #关闭文件写入 ``` 存入cpp后代码 ```cpp #include<iostream> using namespace std; string a[60]={"0","1","3","9","33","153","873","5913","46233","409113","4037913","43954713","522956313","6749977113","93928268313","1401602636313","22324392524313","378011820620313","6780385526348313","128425485935180313","2561327494111820313","53652269665821260313","1177652997443428940313","27029669736328405580313","647478071469567844940313","16158688114800553828940313","419450149241406189412940313","11308319599659758350180940313","316196664211373618851684940313","9157958657951075573395300940313","274410818470142134209703780940313","8497249472648064951935266660940313","271628086406341595119153278820940313","8954945705218228090637347680100940313","304187744744822368938255957323620940313","10637335711130967298604907294846820940313","382630662501032184766604355445682020940313","14146383753727377231082583937026584420940313","537169001220328488991089808037100875620940313","20935051082417771847631371547939998232420940313","836850334330315506193242641144055892504420940313","34289376947494122614363304694584807557656420940313","1439295494700374021157505910939096377494040420940313","61854558558074209658512637979453093884758552420940313","2720126133346522977702138448994068984204397080420940313","122342346998826717539665299944651784048588130840420940313","5624964506810915667389970728744906677010239883800420940313","264248206017979096310354325882356886646207872272920420940313","12678163798554051767172643373255731925167694226950680420940313","620960027832821612639424806694551108812720525606160920420940313","31035053229546199656252032972759319953190362094566672920420940313"}; int main() { int n; cin>>n; cout<<a[n]; } ``` 在考场上，python可以作为工具使用，但不能作为源文件提交，因此用python打表，用c++提交，岂不美哉? ## 正常高精程序 ```cpp #include<iostream> #include<bits/stdc++.h> using namespace std; int a[2000]; int b[2000]; int c[2000]; int sum[2000]; void pplus(int *a,int *c) { int jw=0; for(int i=1;i<=1000;i++) { c[i]+=a[i]+jw; jw=c[i]/10; c[i]%=10; } } void cheng(int *a,int c) { int jw=0; for(int i=1;i<=1000;i++) { a[i]=a[i]*c+jw; jw=a[i]/10; a[i]%=10; } } int main() { int n; cin>>n; a[1]=1; for(int i=1;i<=n;i++) { cheng(a,i); pplus(a,c); } bool flag=0; for(int i=1000;i>=1;i--) { if(c[i]!=0) flag=1; if(flag) cout<<c[i]; } } ``` # 人生苦短，我用py