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fix: handle single node case in pop operation for linked list deque #1824

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fix: handle single node case in pop operation for linked list deque #1824

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21 changes: 12 additions & 9 deletions codes/c/chapter_stack_and_queue/linkedlist_deque.c
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Original file line number Diff line number Diff line change
Expand Up @@ -115,25 +115,28 @@ int pop(LinkedListDeque *deque, bool isFront) {
if (empty(deque))
return -1;
int val;
// 队列长度为 1 时, 头尾指向同一节点
if (deque->queSize == 1) {
val = deque->front->val;
delDoublyListNode(deque->front); // 指向同一节点，释放其一即可
deque->front = NULL;
deque->rear = NULL;
}
// 队首出队操作
if (isFront) {
else if (isFront) {
val = peekFirst(deque); // 暂存头节点值
DoublyListNode *fNext = deque->front->next;
if (fNext) {
fNext->prev = NULL;
deque->front->next = NULL;
}
fNext->prev = NULL;
deque->front->next = NULL;
delDoublyListNode(deque->front);
deque->front = fNext; // 更新头节点
}
// 队尾出队操作
else {
val = peekLast(deque); // 暂存尾节点值
DoublyListNode *rPrev = deque->rear->prev;
if (rPrev) {
rPrev->next = NULL;
deque->rear->prev = NULL;
}
rPrev->next = NULL;
deque->rear->prev = NULL;
delDoublyListNode(deque->rear);
deque->rear = rPrev; // 更新尾节点
}
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21 changes: 12 additions & 9 deletions codes/cpp/chapter_stack_and_queue/linkedlist_deque.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -84,26 +84,29 @@ class LinkedListDeque {
if (isEmpty())
throw out_of_range("队列为空");
int val;
// 队列长度为 1 时, 头尾指向同一节点
if (queSize == 1) {
val = front->val;
delete front; // 指向同一节点，释放其一即可
front = nullptr;
rear = nullptr;
}
// 队首出队操作
if (isFront) {
else if (isFront) {
val = front->val; // 暂存头节点值
// 删除头节点
DoublyListNode *fNext = front->next;
if (fNext != nullptr) {
fNext->prev = nullptr;
front->next = nullptr;
}
fNext->prev = nullptr;
front->next = nullptr;
delete front;
front = fNext; // 更新头节点
// 队尾出队操作
} else {
val = rear->val; // 暂存尾节点值
// 删除尾节点
DoublyListNode *rPrev = rear->prev;
if (rPrev != nullptr) {
rPrev->next = nullptr;
rear->prev = nullptr;
}
rPrev->next = nullptr;
rear->prev = nullptr;
delete rear;
rear = rPrev; // 更新尾节点
}
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25 changes: 14 additions & 11 deletions codes/csharp/chapter_stack_and_queue/linkedlist_deque.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -74,26 +74,29 @@ public void PushLast(int num) {
if (IsEmpty())
throw new Exception();
int? val;
// 队列长度为 1 时, 头尾指向同一节点
if (queSize == 1)
{
val = front!.val;
front = null;
rear = null;
}
// 队首出队操作
if (isFront) {
val = front?.val; // 暂存头节点值
else if (isFront) {
val = front!.val; // 暂存头节点值
// 删除头节点
ListNode? fNext = front?.next;
if (fNext != null) {
fNext.prev = null;
front!.next = null;
}
fNext!.prev = null;
front.next = null;
front = fNext; // 更新头节点
}
// 队尾出队操作
else {
val = rear?.val; // 暂存尾节点值
val = rear!.val; // 暂存尾节点值
// 删除尾节点
ListNode? rPrev = rear?.prev;
if (rPrev != null) {
rPrev.next = null;
rear!.prev = null;
}
rPrev!.next = null;
rear.prev = null;
rear = rPrev; // 更新尾节点
}

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24 changes: 13 additions & 11 deletions codes/dart/chapter_stack_and_queue/linkedlist_deque.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -73,25 +73,27 @@ class LinkedListDeque {
return null;
}
final int val;
if (isFront) {
// 队首出队操作
// 队列长度为 1 时, 头尾指向同一节点
if (_queSize == 1) {
val = _front!.val;
_front = null;
_rear = null;
}
// 队首出队操作
else if (isFront) {
val = _front!.val; // 暂存头节点值
// 删除头节点
ListNode? fNext = _front!.next;
if (fNext != null) {
fNext.prev = null;
_front!.next = null;
}
fNext!.prev = null;
_front!.next = null;
_front = fNext; // 更新头节点
// 队尾出队操作
} else {
// 队尾出队操作
val = _rear!.val; // 暂存尾节点值
// 删除尾节点
ListNode? rPrev = _rear!.prev;
if (rPrev != null) {
rPrev.next = null;
_rear!.prev = null;
}
rPrev!.next = null;
_rear!.prev = null;
_rear = rPrev; // 更新尾节点
}
_queSize--; // 更新队列长度
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20 changes: 11 additions & 9 deletions codes/java/chapter_stack_and_queue/linkedlist_deque.java
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Expand Up @@ -76,25 +76,27 @@ private int pop(boolean isFront) {
if (isEmpty())
throw new IndexOutOfBoundsException();
int val;
// 队列长度为 1 时, 头尾指向同一节点
if (queSize == 1) {
val = front.val;
front = null;
rear = null;
}
// 队首出队操作
if (isFront) {
else if (isFront) {
val = front.val; // 暂存头节点值
// 删除头节点
ListNode fNext = front.next;
if (fNext != null) {
fNext.prev = null;
front.next = null;
}
fNext.prev = null;
front.next = null;
front = fNext; // 更新头节点
// 队尾出队操作
} else {
val = rear.val; // 暂存尾节点值
// 删除尾节点
ListNode rPrev = rear.prev;
if (rPrev != null) {
rPrev.next = null;
rear.prev = null;
}
rPrev.next = null;
rear.prev = null;
rear = rPrev; // 更新尾节点
}
queSize--; // 更新队列长度
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24 changes: 17 additions & 7 deletions codes/javascript/chapter_stack_and_queue/linkedlist_deque.js
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Expand Up @@ -67,13 +67,18 @@ class LinkedListDeque {
return null;
}
const value = this.#rear.val; // 存储尾节点值
// 队列长度为 1 时, 头尾指向同一节点
if (this.#queSize === 1) {
this.#front = null;
this.#rear = null;
}
// 删除尾节点
let temp = this.#rear.prev;
if (temp !== null) {
else {
let temp = this.#rear.prev;
temp.next = null;
this.#rear.prev = null;
this.#rear = temp; // 更新尾节点
}
this.#rear = temp; // 更新尾节点
this.#queSize--;
return value;
}
Expand All @@ -83,14 +88,19 @@ class LinkedListDeque {
if (this.#queSize === 0) {
return null;
}
const value = this.#front.val; // 存储尾节点值
const value = this.#front.val; // 存储头节点值
// 队列长度为 1 时, 头尾指向同一节点
if (this.#queSize === 1) {
this.#front = null;
this.#rear = null;
}
// 删除头节点
let temp = this.#front.next;
if (temp !== null) {
else {
let temp = this.#front.next;
temp.prev = null;
this.#front.next = null;
this.#front = temp; // 更新头节点
}
this.#front = temp; // 更新头节点
this.#queSize--;
return value;
}
Expand Down
20 changes: 11 additions & 9 deletions codes/kotlin/chapter_stack_and_queue/linkedlist_deque.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -67,25 +67,27 @@ class LinkedListDeque {
if (isEmpty())
throw IndexOutOfBoundsException()
val _val: Int
// 队列长度为 1 时, 头尾指向同一节点
if (queSize == 1) {
_val = front!!._val
front = null
rear = null
}
// 队首出队操作
if (isFront) {
else if (isFront) {
_val = front!!._val // 暂存头节点值
// 删除头节点
val fNext = front!!.next
if (fNext != null) {
fNext.prev = null
front!!.next = null
}
fNext!!.prev = null
front!!.next = null
front = fNext // 更新头节点
// 队尾出队操作
} else {
_val = rear!!._val // 暂存尾节点值
// 删除尾节点
val rPrev = rear!!.prev
if (rPrev != null) {
rPrev.next = null
rear!!.prev = null
}
rPrev!!.next = null
rear!!.prev = null
rear = rPrev // 更新尾节点
}
queSize-- // 更新队列长度
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17 changes: 10 additions & 7 deletions codes/python/chapter_stack_and_queue/linkedlist_deque.py
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Original file line number Diff line number Diff line change
Expand Up @@ -64,23 +64,26 @@ def pop(self, is_front: bool) -> int:
"""出队操作"""
if self.is_empty():
raise IndexError("双向队列为空")
# 队列长度为 1 时, 头尾指向同一节点
if self._size == 1:
val: int = self._front.val
self._front = None
self._rear = None
# 队首出队操作
if is_front:
elif is_front:
val: int = self._front.val # 暂存头节点值
# 删除头节点
fnext: ListNode | None = self._front.next
if fnext is not None:
fnext.prev = None
self._front.next = None
fnext.prev = None
self._front.next = None
self._front = fnext # 更新头节点
# 队尾出队操作
else:
val: int = self._rear.val # 暂存尾节点值
# 删除尾节点
rprev: ListNode | None = self._rear.prev
if rprev is not None:
rprev.next = None
self._rear.prev = None
rprev.next = None
self._rear.prev = None
self._rear = rprev # 更新尾节点
self._size -= 1 # 更新队列长度
return val
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19 changes: 10 additions & 9 deletions codes/ruby/chapter_stack_and_queue/linkedlist_deque.rb
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Expand Up @@ -69,25 +69,26 @@ def push_last(num)
def pop(is_front)
raise IndexError, '双向队列为空' if is_empty?

# 队列长度为 1 时, 头尾指向同一节点
if @size == 1
val = @front.val
@front = nil
@rear = nil
# 队首出队操作
if is_front
elsif is_front
val = @front.val # 暂存头节点值
# 删除头节点
fnext = @front.next
unless fnext.nil?
fnext.prev = nil
@front.next = nil
end
fnext.prev = nil
@front.next = nil
@front = fnext # 更新头节点
# 队尾出队操作
else
val = @rear.val # 暂存尾节点值
# 删除尾节点
rprev = @rear.prev
unless rprev.nil?
rprev.next = nil
@rear.prev = nil
end
rprev.next = nil
@rear.prev = nil
@rear = rprev # 更新尾节点
end
@size -= 1 # 更新队列长度
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20 changes: 11 additions & 9 deletions codes/swift/chapter_stack_and_queue/linkedlist_deque.swift
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Expand Up @@ -76,26 +76,28 @@ class LinkedListDeque {
fatalError("双向队列为空")
}
let val: Int
// 队列长度为 1 时, 头尾指向同一节点
if _size == 1 {
val = front!.val
front = nil
rear = nil
}
// 队首出队操作
if isFront {
else if isFront {
val = front!.val // 暂存头节点值
// 删除头节点
let fNext = front?.next
if fNext != nil {
fNext?.prev = nil
front?.next = nil
}
fNext?.prev = nil
front?.next = nil
front = fNext // 更新头节点
}
// 队尾出队操作
else {
val = rear!.val // 暂存尾节点值
// 删除尾节点
let rPrev = rear?.prev
if rPrev != nil {
rPrev?.next = nil
rear?.prev = nil
}
rPrev?.next = nil
rear?.prev = nil
rear = rPrev // 更新尾节点
}
_size -= 1 // 更新队列长度
Expand Down
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