linux c 實現大數相乘

  1 #include <stdio.h>
  2 #include <string.h>
  3 #include <math.h>
  4 #include <stdbool.h>
  5 
  6 #define MAX_LENGTH 128
  7 #define ASSIST_LENGTH 19
  8 
  9 int main(int argc, char **argv)
 10 {
 11     unsigned long long data[MAX_LENGTH] = {0}, tmp = 0;
 12     int i = 0, j = 0, o_len = MAX_LENGTH - ASSIST_LENGTH;
 13     bool c_flag = true;
 14 
 15     if (argc < 3)
 16     {
 17         printf("argument error\n");
 18         return -1;
 19     }
 20 
 21     if (strlen(argv[1]) > o_len)
 22     {
 23         printf("out of range\n");
 24         return -1;
 25     }
 26     
 27     if (strlen(argv[2]) > 19)
 28     {
 29         printf("out of range\n");
 30         return -1;
 31     }
 32     
 33     tmp = atoll(argv[2]);
 34 
 35     if (9223372036854775807ULL == tmp && ('8' == argv[2][18] || '9' == argv[2][18]))
 36     {
 37         printf("out of range\n");
 38         return -1;
 39     }
 40 
 41     for (i = strlen(argv[1])-1; i >= 0; i--)
 42     {
 43         data[j] = argv[1][i] - 48;
 44         j++;
 45     }
 46 
 47     for (i = o_len - 1; i >= 0; i--)
 48     {
 49         if (c_flag && 0 == data[i])
 50         {
 51             continue;
 52         }
 53 
 54         c_flag = false;
 55         printf("%llu", data[i]);
 56     }
 57     printf(" * %llu\n", tmp);
 58 
 59     for (i = 0; i < o_len; i++)
 60     {
 61         if (0 == data[i])
 62         {
 63             continue;
 64         }
 65         
 66         data[i] *= tmp;
 67     }
 68 
 69     for (i = 0; i < o_len; i++)
 70     {
 71         if (0 == data[i])
 72         {
 73             continue;
 74         }
 75         
 76         tmp = data[i];
 77         
 78         for (j = ASSIST_LENGTH-1; j >= 1; j--)
 79         {
 80             data[i+j] += (tmp / (unsigned long long)pow(10,j));
 81             tmp %= (unsigned long long)pow(10,j);
 82         }
 83         
 84         data[i] %= 10;
 85     }
 86 
 87     c_flag = true;
 88     for (i = MAX_LENGTH - 1; i >= 0; i--)
 89     {
 90         if (c_flag && 0 == data[i])
 91         {
 92             continue;
 93         }
 94 
 95         c_flag = false;
 96         printf("%llu", data[i]);
 97     }
 98     printf("\n");
 99     
100     return 0;
101 }

實現了任意大數與 2^64-1以下的數相乘，

兩個任意大數可以將其中一個拆分成多個因數，

兩個大數質數暫未考慮