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

使用一个数组报春被乘数个位与乘数的相乘结果，在左移一位累加保存被乘数十位与乘数的相乘结果，以此类推，数组的下标为i的元素的值拥有权值为10^i，代码如下

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
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;
}

uva10106 - Product