c04b.cpp

此文件可以能帮你求体积

// c04b.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <iostream.h>
#include <iomanip.h>
#include <math.h>

int main(int argc, char* argv[])
{
	// 输入n
	int n;
	cout << "请输入n:";
	cin >> n;
	while ( n < 0 )
	{
		cout << "输入有错，请重输:";
		cin >> n;
	}

	if ( n == 0 )
		return 0;

	// 求n!的位数
	double sum = 1.0;
	for ( int i = 1; i <= n; ++i )
		sum += log10( i );

	int size = (int)sum;

	// 分配数组及初始化
	char* pa = new char[size];
	if (!pa)
	{
		cout << "too large factor of " << size << endl;
		return 0;
	}
	
	pa[0] = 1;
	for ( i = 1; i < size; ++i )
		pa[i] = 0;

	// 求 n!
	double bitcount = 1;
	int begin = 0;
	for ( i = 2; i <= n; ++i )
	{
		long and = 0;
		bitcount += log10(i);
		if ( pa[begin] == 0 )
			begin++;
		
		for ( int j = begin; j < int( bitcount ); j++ )
		{
			and += i * pa[j];
			pa[j] = char( and % 10 );
			and /= 10;
		}
	}

	// 打印n!
	int bit = 0;
	for ( i = size - 1; i >= 0; i-- )
	{
		if ( bit % 50 == 0 )
			cout << endl << " 第"
				<< setw(3) << (bit/50+1) << "个50位:";
		cout << (int)pa[i];
		bit++;
	}
	
	cout << endl;

	delete[] pa;

	return 0;
}