ai_1001.cpp

这是acm上的1001题,高精度数的乘法运算. 因为作业的需要我就做了,想把它给那些入门的朋友们.

#include<iostream.h>
#include<string>
void Multiply(unsigned int[],int&, unsigned int[],int);
void Display(unsigned int[],unsigned int,int);
void main()
{
	int PointLen,n,i,UsedNum,len,temp;
	char R[7],*cp;
	while(cin>>R>>n)
	{
		UsedNum=0;
		unsigned int Result[150]={0},Factor[6],a;
		cp=strchr(R,'.');
		PointLen=strlen(cp)-1;
		i=5;
		while(R[i--]=='0')
		{
			R[i+1]=0;PointLen--;
		}
		while(*(cp-1)!=0)
		{
			*cp=*(cp+1);
			cp++;
		}
		temp=atoi(R);
		itoa(temp,R,10);
		len=strlen(R);
		for (i=0;i<len;i++)
		{
			Factor[6+i-len]=R[i]-'0';
			Result[150+i-len]=Factor[6+i-len];
			UsedNum++;
		}
		for (i=0;i<n-1;i++)
			Multiply(Result,UsedNum,Factor,len);
		Display(Result,UsedNum,PointLen*n);
		strset(R,0);
	}
}
void Multiply(unsigned int Result[],int &UsedNum,unsigned int Factor[],int FactorLen)
{
	int i,j;
	unsigned int temp[150]={0};
	for (i=5;i>5-FactorLen;i--)
	{
		for (j=149;j>149-UsedNum;j--)
		{
		    temp[j+i-5]+=Result[j]*Factor[i];
		    temp[j+i-6]+=temp[i+j-5]/10;
			temp[j+i-5]=temp[i+j-5]%10;
		}
	}
	if(temp[j+i-4]!=0)
	{
		UsedNum=154-i-j;
	}
	else
		UsedNum=153-i-j;
	for (i=149;i>149-UsedNum;i--)
		Result[i]=temp[i];
}
void Display(unsigned int Result[],unsigned int UsedNum,int PL)
{
	int i;
	if(PL==0)
	{
		for (i=150-UsedNum;i<150;i++)
			cout<<Result[i];
		cout<<endl;
		return;
	}
	if(UsedNum>PL)
	{
		for (i=150-UsedNum;i<150-PL;i++)
			cout<<Result[i];
		cout<<'.';
		for (i=150-PL;i<150;i++)
			cout<<Result[i];
		cout<<endl;
	}
	else
	{
		cout<<'.';
		for (i=0;i<PL-UsedNum;i++)
			cout<<'0';
		for (i=150-UsedNum;i<150;i++)
			cout<<Result[i];
		cout<<endl;
	}
}