package main
import (
"fmt"
)
/*
Handles edge cases:
- Validates i and j
- Prevents undefined behavior from shifting by ≥ 64 bits
- Masks M so only the required bits are copied
*/
// Convert unsigned 64‑bit integer to binary string without leading zeros
func toBinary(x uint64) string {
if x == 0 {
return "0"
}
s := ""
for x > 0 {
if x&1 == 1 {
s = "1" + s
} else {
s = "0" + s
}
x >>= 1
}
return s
}
// Copy bits from M into N between bit positions [i, j]
func copyBits(N, M uint64, i, j int) uint64 {
if i < 0 || j < 0 || i > j || j >= 63 {
panic("Invalid bit range")
}
length := j - i + 1
// Mask for bits i..j
mask := ((uint64(1) << length) - 1) << i
// Clear bits i..j in N
Ncleared := N &^ mask
// Take only the needed bits from M and shift into place
Mshifted := (M & ((uint64(1) << length) - 1)) << i
return Ncleared | Mshifted
}
func main() {
/*
N: 100 011111 00
M: 110011
Result: 100 110011 00
*/
N := uint64(0b10001111100)
M := uint64(0b110011)
result := copyBits(N, M, 2, 7)
fmt.Println("N: ", toBinary(N))
fmt.Println("M: ", toBinary(M))
fmt.Println("Result: ", toBinary(result))
}
/*
OUTPUT:
N: 10001111100
M: 110011
Result: 10011001100
*/
