BigNumberPlus大数加法

/*
BigNumberPlus(char* strNumLeft, char* strNumRight)
@author arhaiyun
*/
#include "stdafx.h"
#include <iostream>
#include <assert.h>
#include <string.h>


using namespace std;
char* BigNumberPlus(char* strNumLeft, char* strNumRight)
{
	assert(strNumLeft != NULL && strNumRight != NULL);


	int lenLeft = strlen(strNumLeft);
	int lenRight = strlen(strNumRight);
	
	int maxLen = lenLeft > lenRight ? lenLeft : lenRight;
	
	char* result = new char[maxLen + 2];
	memset(result, 0, sizeof(char) * (maxLen + 2));
	result[0] = '0';
	
	int i = lenLeft - 1;
	int j = lenRight - 1;
	int k = maxLen;
	
	while(i >=0 && j >= 0)
	{
		result[k--] = strNumLeft[i--] + strNumRight[j--] - '0';
	}


	if(i >= 0)
	{
		while(i >= 0)
			result[k--] = strNumLeft[i--];
	}
	
	if(j >= 0)
	{
		while(j >= 0)
			result[k--] = strNumLeft[j--];
	}
	
	for(i = maxLen; i > 0; i--)
	{
		if(result[i] > '9')
		{
			result[i] -= 10;
			result[i - 1] += 1;
		}
	}
	
	size_t pos = strspn(result, "0");


	printf("%s\n", result + pos);
	
	return result;
}




int main(int argc, char* argv[])
{
	char strNum1[] = "7897912345678910";
	char strNum2[] = "98765432189";
	
	BigNumberPlus(strNum1, strNum2);

	system("pause");
	return 0;
}