解一,双指针翻转
pub fn reverse_string(s: &mut Vec<char>) {
	let mut left = 0usize;
	let mut right = s.len() - 1;
	while left < right {
		s.swap(left, right);
		left += 1;
		right -= 1;
	}
}时间: 空间:
pub fn reverse_string(s: &mut Vec<char>) {
	let mut left = 0usize;
	let mut right = s.len() - 1;
	while left < right {
		s.swap(left, right);
		left += 1;
		right -= 1;
	}
}时间: 空间: