大数乘法

# include<stdio.h># include<string.h># include<stdlib.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);}

http://blog.csdn.net/chichangjing1/article/details/8619152