大数相乘

要点:

1，数字用字符串表示

2，纵位相乘，用一个临时整形数组保存中间变量

3，处理整形数组中间结果的进位，将整形数组的结果转化为数组

#include<stdlib.h>

void multiply(char* a, char* b, char* s)
{
	int i, j,*c;
	int aLen = strlen(a);
	int bLen = strlen(b);
	c = (int*)malloc(sizeof(int)*(aLen + bLen));
	for(i = 0; i < aLen + bLen; i++)
	{
		c[i] = 0;
	}
	
	for(i = 0; i < aLen; i++)
	{
		for(j = 0; j < bLen; j++)
		{
			c[i + j + 1] += (a[i] - '0')*(b[j] - '0');
		}
	}
	
	for(i = aLen + bLen - 1; i > 0; i--)
	{
		if(c[i] >= 10)
		{
			c[i-1] += c[i] / 10;
			c[i] = c[i] % 10;		
		}
	}
	i = 0;
	while(c[i] == 0)
		i++;
	for(j = 0; i < aLen + bLen; i++)
	{
		s[j++] = c[i] + '0';
	}
	s[j] = '\0';
	printf("%s",s);
}


int main()
{
	char a[] = "994555567567678675";
	char b[] = "995568578463635365";
	char s[1000];
	multiply(a,b,s);
}