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# Write a method to set all bits between i and j in N equal to M

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Problem statement
You are given two 32-bit numbers, $N$ and $M$, and two bit positions, $i$ and $j$. Write a method to set all bits between $i$ and $j$ in $N$ equal to $M$ (e g , $M$ becomes a substring of $N$ located at $i$ and starting at $j$)

Example
Input: $N = 10000000000$, $M = 10101$, $i = 2$, $j = 6$
Output: $N = 10001010100$

Solution

```public class SetBits {

public static int updateBits(int n, int m, int i, int j) {
int max = ~0; /* All 1’s */

// 1’s through position j, then 0’s
int left = max - ((1 << j) - 1);

System.out.println(Integer.toBinaryString(left));

// 1’s after position i
int right = ((1 << i) - 1);

System.out.println(Integer.toBinaryString(right));

// 1’s, with 0s between i and j
int mask = left | right;

// Clear i through j, then put m in there
return (n & mask) | (m << i);
}

public static void main(String[] args) {
updateBits(1024, 21, 2, 6);
}

}```