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73 lines (63 loc) · 1.88 KB
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import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Scanner;
import org.omg.CORBA.portable.InputStream;
import UI_sizeyunsuan.system;
/*
* 大数乘法
* 参数：
* num1为第一个因数，用字符数组保存
* num2为第二个因数
* sums数组保存相乘的结果，即：num1*num2=sum
* 返回值：返回数组sum的有效长度，即计算结果的位数
*/
public class MaxMultiy {
final static int max=100;
public static void main(String[] args) {
int len;
Scanner sc = new Scanner(System.in);
while(sc.hasNext()) {
String a;
String b;
int sum[] =new int[max*2+10]; // 存放计算的结果，低位在前，高位在后，即sum[0]是低位
//System.out.println("请输入第一个大数：");
a = sc.nextLine();
//System.out.println("请输入第二个大数：");
b = sc.nextLine();
char[] num1 = a.trim().toCharArray();
char[] num2 = b.trim().toCharArray();
len = Multiplication(num1, num2, sum);
for(int i = len-1; i>=0; i--)
System.out.print(sum[i]);
System.out.println();
}
}
static int Multiplication(char num1[],char num2[], int sum[]){
int i, j, len, len1, len2;
int a[]=new int[max+10];
int b[]=new int[max+10];
int c[]=new int[max*2+10];
len1 = (num1).length;
for(j = 0, i = len1-1; i >= 0; i--) //把数字字符转换为整型数
a[j++] = num1[i]-'0';
len2 = (num2).length;
for(j = 0, i = len2-1; i >= 0; i--)
b[j++] = num2[i]-'0';
for(i = 0; i < len2; i++) { //用第二个数乘以第一个数,每次一位
for(j = 0; j < len1; j++){
c[i+j] += b[i] * a[j]; //先乘起来,后面统一进位
}
}
for(i=0; i<max*2; i++){ //循环统一处理进位问题
if(c[i]>=10){
c[i+1]+=c[i]/10;
c[i]%=10;
}
}
for(i = max*2; c[i]==0 && i>=0; i--); //跳过高位的0
len = i+1; // 记录结果的长度
for(; i>=0; i--)
sum[i]=c[i];
return len;
}
}