ex4.4: Incorrect solution

[sherif-fanous]

The exercise requested to write a version of rotate that operates in a single pass. The answer provided rotates a slice by one position to the left, so while your code runs correctly it's not the right answer to the exercise.

Generic solution that performs in place rotation

// Rotates in place the slice s to the left by n steps
func rotateLeft(s []int, n int) {
	if len(s) == 0 || n%len(s) == 0 {
		return
	}

	n = n % len(s)

	ss := make([]int, len(s))

	copy(ss, s)
	copy(s, ss[n:])
	copy(s[len(s)-n:], ss[0:n])
}

Generic solution that doesn't perform in place rotation.

// Rotates the slice s to the left by n steps
func rotateLeft(s []int, n int) []int {
	if len(s) == 0 || n%len(s) == 0 {
		return s
	}

	n = n % len(s)
	s = append(s[n:], s[0:n]...)

	return s
}