大整数相加

http://blog.chinaunix.net/uid-21843387-id-105888.html

#include <iostream>
#include <cstdlib>
using namespace std;
char *AddBigInt(char *str1, char *str2)
{
 int carry = 0; //进位，初始化为0
 int i = strlen(str1) - 1; //指向第一个加数的最低位
 int j = strlen(str2) - 1; //指向第二个加数的最低位
 int maxLen = strlen(str1) >= strlen(str2) ?
  (strlen(str1) + 1) : (strlen(str2) + 1);
 char *result = new char[maxLen + 1];
 result[maxLen] = '\0'; //字符串最后一位为'\0'
 int k = strlen(result) - 1; //指向结果数组的最低位
 while((i >= 0)&&(j >= 0))
 {
  result[k] = ((str1[i] - '0') + (str2[j] - '0' + carry))%10 + '0';
  carry = ((str1[i] - '0') + (str2[j] - '0' + carry))/10;
  --i;
  --j;
  --k;
 }
 while(i >= 0)
 {
  result[k] = ((str1[i] - '0') + carry)%10 + '0';
  carry = ((str1[i] - '0') + carry)/10;
  --i;
  --k;
 }
 while(j >= 0)
 {
  result[k] = ((str2[j] - '0') + carry)%10 + '0';
  carry = ((str2[j] - '0') + carry)/10;
  --j;
  --k;
 }
 result[0] = carry + '0';

 if(result[0] != '0')
  return result;
 else
  return (result + 1);
}
int main()
{
 char num1[] = "123456789323";
 char num2[] = "45671254563123";
 char *result = NULL;
 result = AddBigInt(num1, num2);
 cout<<num1<<" + "<<num2<<" = ";
 cout<<result<<endl;
 return 0;
}