Flatten 2D Vector
Similar Problems:
- Design Compressed String Iterator
- Flatten Nested List Iterator
- Review: Object-Oriented Design Problems
- Tag: oodesign
Implement an iterator to flatten a 2d vector.
For example,
Given 2d vector = [ [1,2], [3], [4,5,6] ]
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,2,3,4,5,6].
Follow up:
As an added challenge, try to code it using only iterators in C++ or iterators in Java.
Github: code.dennyzhang.com
Credits To: leetcode.com
Leave me comments, if you have better ways to solve.
## Blog link: https://code.dennyzhang.com/flatten-2d-vector ## Basic Ideas: Caching current element ## ## Sample Data: some elements may look like [[1], [], [2, 3]] ## Assumption: return None, if unexpected input/call ## ## Complexity: class Vector2D(object): def __init__(self, vec2d): """ Initialize your data structure here. :type vec2d: List[List[int]] """ self.vec2d = vec2d self.row, self.col = 0, 0 def next(self): """ :rtype: int """ if self.hasNext() is False: return None self.col += 1 return self.vec2d[self.row][self.col-1] def hasNext(self): """ :rtype: bool """ while self.row < len(self.vec2d) and self.col == len(self.vec2d[self.row]): self.col, self.row = 0, self.row + 1 return self.row != len(self.vec2d) # Your Vector2D object will be instantiated and called as such: # i, v = Vector2D(vec2d), [] # while i.hasNext(): v.append(i.next())
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