大数加法（利用数组实现）

#include<iostream>
#include<string>
using namespace std;

const int size = 50;

int main()
{
	string s1, s2;
	cin >> s1 >> s2;
	int len = (s1.length()>s2.length()) ? s1.length() : s2.length();

	int a1[size] = { 0 };
	int a2[size] = { 0 };
	int a3[size] = { 0 };

	//用数组储存两个大数
	for (int i = 0; i<s1.length(); i++)
		a1[i] = s1[i] - ‘0‘;
	for (int i = 0; i<s2.length(); i++)
		a2[i] = s2[i] - ‘0‘;

	//进位储存
	int carry = 0;
	
	//结果大数位数储存
	int j = 0;

	//逆序储存结果
	for (int i = len - 1; i >= 0; i--)
	{
		a3[j] = (a1[i] + a2[i] + carry) % 10;
		carry = (a1[i] + a2[i] + carry) / 10;
		j++;
	}
	
	if (carry != 0)
	{
		a3[j] = carry;
		j++;
	}

	//逆序
	for (int i = 0; i < j / 2; i++)
	{
		int temp = a3[i];
		a3[i] = a3[j - i - 1];
		a3[j - i - 1] = temp;
	}
	
	//输出
	for (int i = 0; i < j; i++)
		cout << a3[i];

	cout << endl;

	return 0;
}