Big Number（阶乘）

http://acm.hdu.edu.cn/showproblem.php?pid=1018

 

正确的解法为：

 

#include <iostream>using namespace std;int main(){int t,n,ca,cb,digit;double num;if(cin>>t){for(ca=0;ca<t;ca++){cin>>n;digit=1;num=1;for(cb=2;cb<=n;cb++){num*=cb;if(num<10){ continue;}if(num<100){ digit+=1;num/=10;continue;}if(num<1000){ digit+=2;num/=100;continue;}if(num<10000){ digit+=3;num/=1000;continue;}if(num<100000){ digit+=4;num/=10000;continue;}if(num<1000000){ digit+=5;num/=100000;continue;}if(num<10000000){ digit+=6;num/=1000000;continue;}if(num<100000000){ digit+=7;num/=10000000;continue;}}cout<<digit<<endl;}}return 0;}

 

 

错误的解法为：

#include <iostream>#include <vector>using namespace std;/************************************************************************//* 主要是阶乘溢出，即便是unsigned long long 类型，20的阶乘照样溢出 *//************************************************************************/unsigned long long factorial(int n);int main(){int N;cin>>N;for (int i=0; i<N; i++){int m;cin>>m;long result = factorial(m);printf("%ld/n", result);int sum = 0;while (result != 0){result /= 10;sum++;}printf("%d/n", sum);}}unsigned long long factorial(int n){unsigned long long sum = 1;for (int i=1; i<=n; i++){sum *= i;}return sum;}