UVA 10106 - Product

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本文介绍了一种处理大整数相乘问题的算法实现，该算法能够有效地处理位数超过标准整型变量限制的大整数乘法运算，并通过样例输入输出展示了其正确性和可行性。

10106 - 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

# include <stdio.h>
# include <stdlib.h>
# include <string.h>

#define MAXN 1000

int a[MAXN];
char s1[MAXN], s2[MAXN];

int main ( ){
    int i, j, p, len1, len2;
    while(scanf("%s %s", s1, s2) == 2){
        memset(a, 0, sizeof(a));
        len1 = strlen(s1); len2 = strlen(s2);
        for(i=len1-1; i>=0; i--)
            for(j=len2-1, p=len1-1-i; j>=0; j--){
                a[p++] += (s1[i]-'0')*(s2[j]-'0');
            }
        for(i=0; i<MAXN; i++){
            a[i+1] += a[i]/10;
            a[i] %= 10;
        }

        for(i=MAXN-1; i>=0; i--) if(a[i]) break;
        if(i==-1) printf("0");
        else for(; i>=0; i--) printf("%d", a[i]);
        putchar('\n');
    }

    return 0;
}