comparing bits (one position at a time) - c++

Question

Initially I have user input decimal numbers (0 - 15), and I will turn that into binary numbers.
Say these numbers are written into a text file, as shown in the picture. These numbers are arranged by the numbers of 1's. The dash - is used to separate different groups of 1.
I have to read this file, and compare strings of one group with the all the strings in the group below, i.e., Group 1 with all the strings in group 2, and group 2 - group 3.
The deal is that, only one column of 0 / 1 difference is allowed, and that column is replaced by letter t. If more than one column of difference is encountered, write none.
So say group 2, 0001 with group 3, 0011, only the second column is different. however, 0010 and 0101 are two columns of difference.
The result will be written into another file.....
At the moment, when I am reading these strings, I am using vector string. I came across bitset. What is important is that I have to access the character one at a time, meaning I have break the vector string into vector char. But it seems like there could be easier way to do it.
I even thought about a hash table - linked-list. Having group 1 assigned to H[0]. Each comparison is done as H[current-group] with H[current_group+1]. But beyond the first comparison (comparing 1's and 0's), the comparison beyond that will not work under this hash-linked way. So I gave up on that.
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>
#include <iterator>
using namespace std;
int main() {
ifstream inFile("a.txt");
vector<string> svec;
copy(istream_iterator<string>(inFile), istream_iterator<string>(), back_inserter(svec));
copy(svec.begin(), svec.end(), ostream_iterator<string>(cout,"\n"));
for(int i = 0; i < svec.size(); i++)
{
cout << svec[i] << " ";
}
inFile.close();
return 0;
}
This is the sample code of writing it into a file....but like I said, the whole deal of vector seems impractical in my case....
Any help is appreciated. thanks

Answer 1

I don't understand your code snippet -- it looks like all it does is read in the input file into a vector of strings, which will then contain each whitespace-delimited word in a separate string, then write it back out in 2 different ways (once with words separated by \n, once with them separated by spaces).
It seems the main problem you're having is with reading and interpreting the file itself, as opposed to doing the necessary calculations -- right? That's what I hope this answer will help you with.
I think the line structure of the file is important -- right? In that case you would be better off using the global getline() function in the <string> header, which reads an entire line (rather than a whitespace-delimited word) into a string. (Admittedly that function is pretty well-hidden!) Also you don't actually need to read all the lines into a vector, and then process them -- it's more efficient and actually easier to distill them down to numbers or bitsets as you go:
vector<unsigned> last, curr; // An unsigned can comfortably hold 0-15
ifstream inf("a.txt");
while (true) {
string line;
getline(inf, line); // This is the group header: ignore it
while (getline(inf, line)) {
if (line == "-") {
break;
}
// This line contains a binary string: turn it into a number
// We ignore all characters that are not binary digits
unsigned val = 0;
for (int i = 0; i < line.size(); ++i) {
if (line[i] == '0' || line[i] == '1') {
val = (val << 1) + line[i] - '0';
}
}
curr.push_back(val);
}
// Either we reached EOF, or we saw a "-". Either way, compare
// the last 2 groups.
compare_them_somehow(curr, last); // Not doing everything for you ;)
last = curr; // Using swap() would be more efficient, but who cares
curr.clear();
if (inf) {
break; // Either the disk exploded, or we reached EOF, so we're done.
}
}

Answer 2

Perhaps I've misunderstood your goal, but strings are amenable to array member comparison:
string first = "001111";
string next = "110111";
int sizeFromTesting = 5;
int columnsOfDifference = 0;
for ( int UU = sizeFromTesting; UU >=0; UU-- )
{
if ( first[ UU ] != next[ UU ] )
columnsOfDifference++;
}
cout << columnsOfDifference;
cin.ignore( 99, '\n' );
return 0;
Substitute file streams and bound protection where appropriate.
Not applicable, but to literally bitwise compare variables, & both using a mask for each digit (000010 for second digit).
If or = 0, they match: both are 0. If they or = 1 and & = 1, that digit is 1 for both. Otherwise they differ. Repeat for all the bits and all the numbers in the group.

Answer 3

in vb.net
'group_0 with group_1
If (group_0_count > 0 AndAlso group_1_count > 0) Then
Dim result = ""
Dim index As Integer = 0
Dim g As Integer = 0
Dim h As Integer = 0
Dim i As Integer = 0
For g = 0 To group_0_count - 1
For h = 0 To group_1_count - 1
result = ""
index = 0
For i = 0 To 3
If group_1_0.Items(g).ToString.Chars(i) <> group_1_1.Items(h).ToString.Chars(i) Then
result &= "-"
index = index + 1
Else
result &= group_1_0.Items(g).ToString.Chars(i)
End If
Next
Next
Next
End If

Answer 4

Read it in as an integer, then all you should need is comparisons with bitshifts and bit masks.