Binary addition of Strings

Question

I need to combine an array of strings as below ( so as each character in the result string is a bitwise & of the characters in the input string)

String a = "10110001" String b = "01101101" String c = "10101011" String result = "00100001"

Solution I came up with:

long resultLong = 0; for( String a : inputs ) { resultLong = resultLong & Long.parseLong( a ,2); } String result = Long.toBinaryString( resultLong );

The number of characters in the input string could be very long, and the above solution wouldn't work (NumberFormatException) . I couldn't get my head around how to implement this, what would be the cleanest way ?

How long is very long?

khelwood
– khelwood

2019-09-05 10:56:10 +00:00
Commented Sep 5, 2019 at 10:56 — khelwood
– khelwood, Commented Sep 5, 2019 at 10:56
@khelwood 3600 characters

Chillax
– Chillax

2019-09-05 11:17:35 +00:00
Commented Sep 5, 2019 at 11:17 — Chillax
– Chillax, Commented Sep 5, 2019 at 11:17

Amit Bera · Accepted Answer · 2019-09-05 11:07:54Z

3

If Long is not enough for your use case then you can use BigInteger

BigInteger(String val, int radix);

Which takes a String and radix as the arguments.

BigInteger result = new BigInteger(inputs[0], 2); for (int i = 1; i < inputs.length; i++) { result = result.and(new BigInteger(inputs[i], 2)); } String resultStr = result.toString(2);

edited Sep 5, 2019 at 11:07

answered Sep 5, 2019 at 10:59

Amit Bera

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4 Comments

Chillax Over a year ago

This gives me the op 100001 for the input I have given in my question, so missing the leading 0's

khelwood Over a year ago

@Chillax 100001 is the correct answer. You can pad it with leading zeroes if you need it to be of your expected length.

Chillax Over a year ago

@khelwood Clear

B. Go Over a year ago

It's nice to notice that the result can be computed bit per bit (or char per char, if you prefer), so the maximum length of numeric values shouldn't have anything to do with the answer...

Shubhendu Pramanik · Accepted Answer · 2019-09-05 11:27:33Z

Here's your algorithm. This will work for any number of Strings provided that all the Strings are of same length:

public static void main(String[] args) { String a = "10110001"; String b = "01101101"; String c = "10101011"; String arr[] = new String[]{a, b, c}; String finalString = ""; for (int i = 0; i < arr[0].length(); i++) { int temp = Integer.parseInt("" + arr[0].charAt(i)); for (int j = 1; j < arr.length; j++) { temp = temp & Integer.parseInt("" + arr[j].charAt(i)); } finalString += temp; } System.out.println(finalString); }

O/P

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