Peeking Iterator – LeetCode Solution Java , Python 3, Python 2 , C , C++, Best and Optimal Solutions , All you need.
Design an iterator that supports the peek
operation on an existing iterator in addition to the hasNext
and the next
operations.
Implement the PeekingIterator
class:
PeekingIterator(Iterator<int> nums)
Initializes the object with the given integer iteratoriterator
.int next()
Returns the next element in the array and moves the pointer to the next element.boolean hasNext()
Returnstrue
if there are still elements in the array.int peek()
Returns the next element in the array without moving the pointer.
Note: Each language may have a different implementation of the constructor and Iterator
, but they all support the int next()
and boolean hasNext()
functions.
Example 1:
Input ["PeekingIterator", "next", "peek", "next", "next", "hasNext"] [[[1, 2, 3]], [], [], [], [], []] Output [null, 1, 2, 2, 3, false] Explanation PeekingIterator peekingIterator = new PeekingIterator([1, 2, 3]); // [1,2,3] peekingIterator.next(); // return 1, the pointer moves to the next element [1,2,3]. peekingIterator.peek(); // return 2, the pointer does not move [1,2,3]. peekingIterator.next(); // return 2, the pointer moves to the next element [1,2,3] peekingIterator.next(); // return 3, the pointer moves to the next element [1,2,3] peekingIterator.hasNext(); // return False
Constraints:
1 <= nums.length <= 1000
1 <= nums[i] <= 1000
- All the calls to
next
andpeek
are valid. - At most
1000
calls will be made tonext
,hasNext
, andpeek
.
C++ Peeking Iterator LeetCode Solution
class PeekingIterator : public Iterator
{
public:
PeekingIterator(const vector<int> &nums) : Iterator(nums)
{
}
int peek()
{
return Iterator(*this).next();
}
int next()
{
return Iterator::next();
}
bool hasNext() const
{
return Iterator::hasNext();
}
};
Java Peeking Iterator LeetCode Solution
class PeekingIterator implements Iterator<Integer> {
Iterator<Integer> iter = null;
Integer next = null;
public PeekingIterator(Iterator<Integer> iterator) {
// initialize any member here.
iter = iterator;
if(hasNext()) next = iter.next();
}
// Returns the next element in the iteration without advancing the iterator.
public Integer peek() {
return next;
}
// hasNext() and next() should behave the same as in the Iterator interface.
// Override them if needed.
@Override
public Integer next() {
Integer currVal = next;
if(iter.hasNext())
next = iter.next();
else
next = null;
return currVal;
}
@Override
public boolean hasNext() {
return next != null || iter.hasNext();
}
}
Python 3 Peeking Iterator LeetCode Solution
class PeekingIterator(object):
def __init__(self, iterator):
self.iter = iterator
self.temp = self.iter.next() if self.iter.hasNext() else None
def peek(self):
return self.temp
def next(self):
ret = self.temp
self.temp = self.iter.next() if self.iter.hasNext() else None
return ret
def hasNext(self):
return self.temp is not None
Array-1180
String-562
Hash Table-412
Dynamic Programming-390
Math-368
Sorting-264
Greedy-257
Depth-First Search-256
Database-215
Breadth-First Search-200
Tree-195
Binary Search-191
Matrix-176
Binary Tree-160
Two Pointers-151
Bit Manipulation-140
Stack-133
Heap (Priority Queue)-117
Design-116
Graph-108
Simulation-103
Prefix Sum-96
Backtracking-92
Counting-86
Sliding Window-73
Linked List-69
Union Find-66
Ordered Set-48
Monotonic Stack-47
Recursion-43
Trie-41
Binary Search Tree-40
Divide and Conquer-40
Enumeration-39
Bitmask-37
Queue-33
Memoization-32
Topological Sort-31
Geometry-30
Segment Tree-27
Game Theory-24
Hash Function-24
Binary Indexed Tree-21
Interactive-18
Data Stream-17
String Matching-17
Rolling Hash-17
Shortest Path-16
Number Theory-16
Combinatorics-15
Randomized-12
Monotonic Queue-9
Iterator-9
Merge Sort-9
Concurrency-9
Doubly-Linked List-8
Brainteaser-8
Probability and Statistics-7
Quickselect-7
Bucket Sort-6
Suffix Array-6
Minimum Spanning Tree-5
Counting Sort-5
Shell-4
Line Sweep-4
Reservoir Sampling-4
Eulerian Circuit-3
Radix Sort-3
Strongly Connected Componen-t2
Rejection Sampling-2
Biconnected Component-1
Leave a comment below