Design and implement an iterator to flatten a 2d vector. It should support the following operations: next
and hasNext
.
Example:
Vector2D iterator = new Vector2D([[1,2],[3],[4]]); iterator.next(); // return 1 iterator.next(); // return 2 iterator.next(); // return 3 iterator.hasNext(); // return true iterator.hasNext(); // return true iterator.next(); // return 4 iterator.hasNext(); // return false
Notes:
next()
call will always be valid, that is, there will be at least a next element in the 2d vector when next()
is called.
Follow up:
As an added challenge, try to code it using only iterators in C++ or iterators in Java.
struct Vector2D {
array: Vec<i32>,
count: usize,
}
impl Vector2D {
fn new(v: Vec<Vec<i32>>) -> Self {
let mut array = vec![];
for row in v {
for col in row {
array.push(col);
}
}
Vector2D { array, count: 0 }
}
fn next(&mut self) -> i32 {
let res = self.array[self.count];
self.count += 1;
res
}
fn has_next(&self) -> bool {
self.count < self.array.len()
}
}
#[test]
fn test() {
let v = vec![vec![1, 2], vec![3], vec![4]];
let mut obj = Vector2D::new(v);
assert_eq!(obj.next(), 1);
assert_eq!(obj.next(), 2);
assert_eq!(obj.next(), 3);
assert_eq!(obj.has_next(), true);
assert_eq!(obj.has_next(), true);
assert_eq!(obj.next(), 4);
assert_eq!(obj.has_next(), false);
}