641.设计循环双端队列

一、题目描述

设计实现双端队列。
你的实现需要支持以下操作:

  • MyCircularDeque(k):构造函数,双端队列的大小为k。
  • insertFront():将一个元素添加到双端队列头部。 如果操作成功返回 true。
  • insertLast():将一个元素添加到双端队列尾部。如果操作成功返回 true。
  • deleteFront():从双端队列头部删除一个元素。 如果操作成功返回 true。
  • deleteLast():从双端队列尾部删除一个元素。如果操作成功返回 true。
  • getFront():从双端队列头部获得一个元素。如果双端队列为空,返回 -1。
  • getRear():获得双端队列的最后一个元素。 如果双端队列为空,返回 -1。
  • isEmpty():检查双端队列是否为空。
  • isFull():检查双端队列是否满了。

示例:

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MyCircularDeque circularDeque = new MycircularDeque(3); // 设置容量大小为3
circularDeque.insertLast(1); // 返回 true
circularDeque.insertLast(2); // 返回 true
circularDeque.insertFront(3); // 返回 true
circularDeque.insertFront(4); // 已经满了,返回 false
circularDeque.getRear(); // 返回 2
circularDeque.isFull(); // 返回 true
circularDeque.deleteLast(); // 返回 true
circularDeque.insertFront(4); // 返回 true
circularDeque.getFront(); // 返回 4

提示:

  • 所有值的范围为 [1, 1000]
  • 操作次数的范围为 [1, 1000]
  • 请不要使用内置的双端队列库。

二、题解

1.算法描述

  • 队列

2.个人分析

  1. 注意循环队列要对队列长度取余
  2. 多申请一个空间用于判断队列是否已满

3.代码

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typedef struct
{
int *data;
int front;
int rear;
int length;
} MyCircularDeque;

/** Initialize your data structure here. Set the size of the deque to be k. */

MyCircularDeque *myCircularDequeCreate(int k)
{
MyCircularDeque *obj = malloc(sizeof(MyCircularDeque) * (k + 1));
obj->data = malloc(sizeof(int) * (k + 1));
obj->front = 0;
obj->rear = 0;
obj->length = k + 1;
return obj;
}
//函数声明,才能调用
bool myCircularDequeIsFull(MyCircularDeque *obj);
bool myCircularDequeIsEmpty(MyCircularDeque *obj);
/** Adds an item at the front of Deque. Return true if the operation is successful. */
bool myCircularDequeInsertFront(MyCircularDeque *obj, int value)
{
if (myCircularDequeIsFull(obj))
return false;
int pos = (obj->front + obj->length - 1) % obj->length;
obj->data[pos] = value;
obj->front = pos;
return true;
}

/** Adds an item at the rear of Deque. Return true if the operation is successful. */
bool myCircularDequeInsertLast(MyCircularDeque *obj, int value)
{
if (myCircularDequeIsFull(obj))
return false;
obj->data[obj->rear] = value;
obj->rear = (obj->rear + 1) % obj->length;
return true;
}

/** Deletes an item from the front of Deque. Return true if the operation is successful. */
bool myCircularDequeDeleteFront(MyCircularDeque *obj)
{
if (myCircularDequeIsEmpty(obj))
return false;
obj->front = (obj->front + 1) % obj->length;
return true;
}

/** Deletes an item from the rear of Deque. Return true if the operation is successful. */
bool myCircularDequeDeleteLast(MyCircularDeque *obj)
{
if (myCircularDequeIsEmpty(obj))
return false;
obj->rear = (obj->rear - 1 + obj->length) % obj->length;
return true;
}

/** Get the front item from the deque. */
int myCircularDequeGetFront(MyCircularDeque *obj)
{
if (myCircularDequeIsEmpty(obj))
return -1;
return obj->data[obj->front];
}

/** Get the last item from the deque. */
int myCircularDequeGetRear(MyCircularDeque *obj)
{
if (myCircularDequeIsEmpty(obj))
return -1;
int pos = (obj->rear + obj->length - 1) % obj->length;
return obj->data[pos];
}

/** Checks whether the circular deque is empty or not. */
bool myCircularDequeIsEmpty(MyCircularDeque *obj)
{
if (obj->front == obj->rear)
return true;
return false;
}

/** Checks whether the circular deque is full or not. */
bool myCircularDequeIsFull(MyCircularDeque *obj)
{
if (obj->front == (obj->rear + 1) % obj->length)
return true;
return false;
}

void myCircularDequeFree(MyCircularDeque *obj)
{
free(obj);
return;
}

/**
* Your MyCircularDeque struct will be instantiated and called as such:
* MyCircularDeque* obj = myCircularDequeCreate(k);
* bool param_1 = myCircularDequeInsertFront(obj, value);

* bool param_2 = myCircularDequeInsertLast(obj, value);

* bool param_3 = myCircularDequeDeleteFront(obj);

* bool param_4 = myCircularDequeDeleteLast(obj);

* int param_5 = myCircularDequeGetFront(obj);

* int param_6 = myCircularDequeGetRear(obj);

* bool param_7 = myCircularDequeIsEmpty(obj);

* bool param_8 = myCircularDequeIsFull(obj);

* myCircularDequeFree(obj);
*/