leetcode-algorithms/src/PeekingIterator.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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// https://leetcode.com/problems/peeking-iterator

// T: O(N)

// S: O(N)

import java.util.Iterator;

public class PeekingIterator implements Iterator<Integer> {

final private Iterator<Integer> iterator;

int next;

boolean hasNext;

public PeekingIterator(Iterator<Integer> iterator) {

this.iterator = iterator;

hasNext = iterator.hasNext();

next = iterator.hasNext() ? iterator.next() : 0;

}

// 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() {

int result = next;

hasNext = iterator.hasNext();

next = iterator.hasNext() ? iterator.next() : 0;

return result;

}

@Override

public boolean hasNext() {

return hasNext;

}

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