平方乘算法实现

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

#define DECDATATYPE long
#define BINDATATYPE char

typedef struct bin_data{
    BINDATATYPE data;
    struct bin_data *next;    
}BIN_DATA;

BIN_DATA *head;

void dec_to_bin(DECDATATYPE dec_num){
    BIN_DATA *p,*q;
    if((head=(BIN_DATA *)malloc(sizeof(BIN_DATA)))==NULL){
        printf("No free mem to allloc.\n");
        exit(0);
    }
    head->data = '\0';
    head->next = NULL;
    p=head;
    
    while(dec_num){
        /* insert to the back of head node */
        q=(BIN_DATA *)malloc(sizeof(BIN_DATA));
        q->data = (BINDATATYPE)(dec_num & 0x1);
        q->next = p->next;
        p->next = q;
        
        /* append node to the end of list 
        q=(BIN_DATA *)malloc(sizeof(BIN_DATA));
        q->data = (BINDATATYPE)(dec_num & 0x1);
        q->next = NULL;
        p->next = q;
        p = q;
        */
        dec_num = dec_num >> 1;
    }
}

DECDATATYPE square_multi(DECDATATYPE base_num, DECDATATYPE exp_num, DECDATATYPE mod_num){
    DECDATATYPE result=1;
    BIN_DATA *p;
    
    dec_to_bin(exp_num);
    p=head->next;
    
    while(p){
        result=result*result%mod_num;
        if(p->data) result=result*base_num%mod_num;
        p=p->next;
    }
    
    return result;
}

int main (int argc, char * argv[]) {
    DECDATATYPE base_num, exp_num, mod_num;
    
    if(argc < 3) {
        printf("args error.\n");
        return 1;
    }
    
    base_num=atoi(argv[1]);
    exp_num=atoi(argv[2]);
    mod_num=atoi(argv[3]);
    
    printf("The mode value of base[%ld],exp[%ld],mod[%ld] is: [%ld]",base_num,exp_num,mod_num,square_multi(base_num,exp_num,mod_num));
    
    return 0;
}