## Friday, January 2, 2015

### Inserting a number's bits into another 32 bit number at a specified position. [Java]

Q. You are given two 32-bit numbers, N and M, and two bit positions, i and j. Write a method to insert M into N such that M starts at bit j and ends at bit i. You can assume that the bits j through i have enough space to fit all of M. That is, if M = 10011, you can assume that there are at least 5 bits between j and i. You would not, for example, have j = 3 and i = 2, because M could not fully fit between bit 3 and bit 2.

EXAMPLE

Input:    N = 10000000000, M = 10011, i = 2, j = 6
Output:   N = 10001001100

Source:

```public class Code{
static int change(int N, int M, int i, int j){
return ((~(-1>>>(31-(j-i))<<i))&N)|(M<<i);
}

public static void main(String[] args){
int N = (int)Long.parseLong("10110011001100111111001111111100", 2);
int M = Integer.parseInt("110011", 2);
System.out.println(Integer.toBinaryString(change(N, M, 17, 22)));

N = Integer.parseInt("10000000000", 2);
M = Integer.parseInt("10011", 2);
System.out.println(Integer.toBinaryString(change(N, M, 2, 6)));
}
}```

Output:

10110011011001111111001111111100
10001001100