package LeetCode_284
/**
* 284. Peeking Iterator
* https://leetcode.com/problems/peeking-iterator/
* Design an iterator that supports the peek operation on a list in addition to the hasNext and the next operations.
Implement the PeekingIterator class:
PeekingIterator(int[] nums): Initializes the object with the given integer array nums.
int next(): Returns the next element in the array and moves the pointer to the next element.
bool hasNext(): Returns true if there are still elements in the array.
int peek(): Returns the next element in the array without moving the pointer.
* */
// Kotlin Iterator reference:
// https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-iterator/
class PeekingIterator(iterator: Iterator<Int>) : Iterator<Int> {
private var isDone = false
private var it: Iterator<Int>? = null
private var next: Int = 0
init {
it = iterator
if (iterator.hasNext()){
next = iterator.next()
} else {
isDone = true
}
}
fun peek(): Int {
return next
}
override fun next(): Int {
//return value and move the pointer
val result = next
if (it?.hasNext()!!) {
next = it?.next()!!
} else {
isDone = true
}
return result
}
override fun hasNext(): Boolean {
return !isDone
}
}
/**
* Your PeekingIterator object will be instantiated and called as such:
* var obj = PeekingIterator(arr)
* var param_1 = obj.next()
* var param_2 = obj.peek()
* var param_3 = obj.hasNext()
*/
类似的设计模式：迭代子模式