大数相乘

//大数相乘
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <iostream.h>
void multiply(char* a,char* b,char* c)
{
int i,j,ca,cb,* s;
ca=strlen(a);
cb=strlen(b);
s=(int*)malloc(sizeof(int)*(ca+cb));
for (i=0;i<ca+cb;i++)
s[i]=0;
for (i=0;i<ca;i++)
for (j=0;j<cb;j++)
s[i+j+1]+=(a[i]-'0')*(b[j]-'0');
for (i=ca+cb-1;i>=0;i--)
if (s[i]>=10)
{
s[i-1]+=s[i]/10;
s[i]%=10;
}
i=0;
while (s[i]==0)
i++;
for (j=0;i<ca+cb;i++,j++)
c[j]=s[i]+'0';
c[j]='\0';
free(s);
}
void main()
{
char a[] = "123";
char b[] = "456";
char c[6];
multiply(a,b,c);
cout<<c<<endl;
}

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