Product

The Problem

The problem is to multiply two integers X, Y. (0<=X,Y<10²⁵⁰)

The Input

The input will consist of a set of pairs of lines. Each line in pair contains one multiplyer.

The Output

For each input pair of lines the output line should consist one integer the product.

Sample Input

12
12
2
222222222222222222222222

Sample Output

144
444444444444444444444444

使用一個數組報春被乘數個位與乘數的相乘結果，在左移一位累加保存被乘數十位與乘數的相乘結果，以此類推，數組的下標為i的元素的值擁有權值為10^i，代碼如下

#include
#include
#include
#include
using namespace std;

#define MAX 1000000
int ans[MAX];

int main(void){
	string str1, str2;

#ifndef ONLINE_JUDGE
	freopen("f:\\infile.txt", "r", stdin);
#endif

	while(cin >> str1 >> str2){
		int i;

		memset(ans, 0, sizeof(ans));
		for(i = str1.size()-1; i >= 0; i--){
			for(int j = str2.size()-1, p = str1.size()-1-i; j >=0; j--, p++){
				ans[p] += (str1[i]-'0')*(str2[j]-'0');
			}
		}

		for(i = 0; i < MAX; i++){
			ans[i+1] += ans[i]/10;
			ans[i] = ans[i]%10;
		}

		for(i = MAX-1; i >=0; i--){
			if(ans[i])
				break;
		}
		if(i == -1)
			cout << 0 << endl;
		else{
			for(int j = i; j >= 0; j--){
				cout << ans[j];
			}
			cout << endl;
		}
	}
	return 0;
}