2016腾讯在线模拟笔试-大数乘法

Posted 2020-06-29

首先将参与计算的数组反转，然后计算每一位的乘积，最后再进位。

 1 #include<stdio.h>
 2 #include<memory.h>
 3 #define N 8
 4 #define M 5
 5 void carry_bit(int *x);
 6 void reverse(int *x,int t);
 7 
 8 int main()
 9 {
10     int a[N] = { 4,3,2,1,9,4,6,8 };
11     int b[M] = { 8,9,6,5,6};
12     int c[M+N];
13     memset(c,0,sizeof(int)*(M+N));
14     reverse(a, sizeof(a)/sizeof(int));
15     reverse(b, sizeof(b)/sizeof(int));
16     
17     for (int i = 0; i < N; i++)
18         for (int j = 0; j < M; j++)
19         {
20             c[i + j] += a[i] * b[j];        
21         }
22 
23     carry_bit(c);
24     for (int i = M + N - 1; i >= 0; i--)
25         printf("%d", c[i]);
26     printf("\n");
27 }
28 void carry_bit(int *x)
29 {
30     while (*x++ > 10)
31     {
32         int temp = *(x - 1);
33         *(x - 1) = temp % 10;
34         *x += temp / 10;
35     }
36 }
37 void reverse(int *x,int t)
38 {
39     for (int i = 0; i < t/2; i++)
40     {
41         int temp;
42         temp = *(x+i);
43         *(x+i) = *(x +(t-i-1));
44         *(x +(t-i-1)) = temp;
45     }
46 }