CC150 5.1

5_1.cpp

/* CC150 5.1
 * 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 = 100|0000|0000, M = 10011, i = 2, j = 6
 * Output: N = 100|0100|1100
 */

#include <iostream>

using namespace std;

int insert(int M, int N, int i, int j)
{
	for (int k = 0; i <= j; ++k, ++i) {
		N &= (~(1 << i));
		N |= ((M & (1 << k)) << (i - k));
	}
	return N;
}

int insert2(int M, int N, int i, int j)
{
	int left = ~0 << (j + 1);
	int right = (1 << i) - 1;
	return N & (left | right) | (M << i);
}

int main()
{
	int M, N;
	cin >> M >> N;
	int i, j;
	cin >> i >> j;
	cout << insert(M, N, i, j) << endl;
	cout << insert2(M, N, i, j) << endl;
	return 0;
}