大数相乘.txt

里面包括了一些acm比赛是常用的函数

char a[maxv], b[maxv], d[maxv];
char c[maxv+maxv+1];

void multi(char *a, char *b, char *d)//d=a*b
{
	int i, j, k, lena= strlen(a), lenb = strlen(b), lc = lena+lenb;
	char car, te;
	
	for(i=0; i<=lc; i++) c[i] = 0;
	for( i=lena-1; i>=0; i-- )
	{	for( car=0,j=lenb-1; j>=0; j-- )
		{	
k = i+j+2; te = c[k] + (a[i]-'0')*(b[j]-'0') + car;
			c[k] = te%10, car = te/10;
		}
		if( car ) c[i+j+2] += car;
	}
	
	i=0; while( c[i] == 0 && i<=lc) i++;
	if( i>lc ) strcpy(d,"0");
	else for( j=0, d[lc-i+1]=0; i<=lc; i++,j++ ) d[j] = c[i]+'0';
}