The inputs:
string a = "10101100" __> int
string b = "10010011"
the length of binary number is n = 8
The below codes is to initialize the inputs
// input
#include <iostream>
#include <iomanip>
using namespace std;
const int len = 20;
void trans_string_to_array(string a , int n , int arr[]);
void display_array(int arr[], int len);
int main()
{
// initialization of the array stuff
string a = "10101100";
string b = "10010011";
int n = 8;
int X[len],Y[len],Z[len]; //The first array is to receive the elements in string a and the others so on ,Z = a * b
// transform the string type into array type(in reversed order)
trans_string_to_array(a, n, X);
trans_string_to_array(b, n, Y);
// to display the array to see whether its correct or not
display_array(X, len);
display_array(Y, len);
return 0;
}
void trans_string_to_array(string a , int n , int arr[])
{
for(int i =0; i < n ; ++i){
arr[i] = int(a[n-1-i] - '0'); // you have to transform the char type into int, otherwise it will show its ASCII value
}
for( int i = n; i < len; ++i){
arr[i] = 0;
}
}
void display_array(int arr[], int len)
{
for(int i = 0 ; i < len; ++i){
cout<< setw(3) << arr[i] ;
}
cout << endl;
}
The outpus of the initialization:
0 0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0
1 1 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
Process returned 0 (0x0) execution time : 0.080 s
Press any key to continue.The wrong codes:
#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
void transform_string_to_array(string a, int arr[], int n);
void dis_array(int arr[]);
void multiplication(int arr1[], int arr2[], int arr3[], int n);
void get_high(int arr[], int arr_high[], int n);
void get_low(int arr[], int arr_low[], int n);
int transform_2_to_10(int arr[], int n);
void transform_10_to_2(int x, int arr[]);
const int len = 20;
int main()
{
int n = 8;
string a = "10101100";
string b = "10010011";
int arr1[len], arr2[len], arr3[len];
transform_string_to_array(a, arr1, n);
transform_string_to_array(b, arr2, n);
cout << "The content of arr1:"<< endl;
dis_array(arr1);
cout << transform_2_to_10(arr1, len) << endl;
cout << "The content of arr2:" << endl;
dis_array(arr2);
cout << transform_2_to_10(arr2,len) << endl;
multiplication(arr1, arr2, arr3, n);
dis_array(arr3);
cout << endl << transform_2_to_10(arr3,len);
return 0;
}
void transform_string_to_array(string a, int arr[], int n)
{
int i;
for(i = 0; i<n; ++i){
arr[i] = int(a[n-1-i] - '0');
}
for(int j = i; j < len; ++j){
arr[j] = 0;
}
}
void dis_array(int arr[])
{
for( int i = len-1; i >=0; --i){
cout << setw(3) << arr[i];
}
cout <<endl;
}
void multiplication(int arr1[], int arr2[], int arr3[], int n)
{
if(n==1){
arr3[0] = arr1[0] * arr2[0];
return;
}
for(int i =0; i<len; ++i){
arr3[i] = 0;
}
int arr1_high[len], arr1_low[len], arr2_high[len], arr2_low[len];
get_high(arr1, arr1_high, n );
get_low(arr1, arr1_low, n);
get_high(arr2, arr2_high, n);
get_low(arr2, arr2_low, n);
int part1[len], part2[len], part3[len], part4[len];
int middle = n/2;
multiplication(arr1_high, arr2_high, part1, middle);
multiplication(arr1_high, arr2_low, part2, middle);
multiplication(arr1_low, arr2_high, part3, middle);
multiplication(arr1_low, arr2_low, part4, middle);
int d1, d2, d3, d4;
d1 = transform_2_to_10(part1, len);
d2 = transform_2_to_10(part2, len);
d3 = transform_2_to_10(part3, len);
d4 = transform_2_to_10(part4, len);
int final_result;
final_result = d1*(int)pow(2.0, n) + (d2 + d3)*(int)pow(2.0, n/2) + d4;
transform_10_to_2(final_result, arr3);
}
void get_high(int arr[], int arr_high[], int n)
{
int i;
for(i =0; i<len; ++i){
arr_high[i] = 0;
}
for(i = n/2; i<n; i++){
arr_high[i] = arr[i];
}
}
void get_low(int arr[], int arr_low[], int n)
{
int middle = n/2;
for( int i = 0; i< middle; ++i){
arr_low[i] = arr[i];
}
for(int j = middle; j <len; ++j){
arr_low[j] = 0;
}
arr_low[middle] = '\0';
}
int transform_2_to_10(int arr[], int n)
{
int result = 0;
for(int i =0; i<n; ++i){
result += arr[i]*pow(2.0, i);
}
return result;
}
void transform_10_to_2(int x, int arr[])
{
int i, j=0;
while(x !=0){
arr[j] = x%2;
++j;
x = x/2;
}
for(i =j; i < len; ++i){
arr[j] = 0;
}
}
The wrong anwser, I wish I could find the reason behind it.
The content of arr1:
0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 1 1 0 0
172
The content of arr2:
0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 1 1
147
-1 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-573440