关于leetcode:leetcode队列之设计循环双端队列

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本文次要记录一下 leetcode 队列之设计循环双端队列

题目

 设计实现双端队列。你的实现须要反对以下操作：MyCircularDeque(k)：构造函数, 双端队列的大小为 k。insertFront()：将一个元素增加到双端队列头部。如果操作胜利返回 true。insertLast()：将一个元素增加到双端队列尾部。如果操作胜利返回 true。deleteFront()：从双端队列头部删除一个元素。如果操作胜利返回 true。deleteLast()：从双端队列尾部删除一个元素。如果操作胜利返回 true。getFront()：从双端队列头部取得一个元素。如果双端队列为空，返回 -1。getRear()：取得双端队列的最初一个元素。如果双端队列为空，返回 -1。isEmpty()：查看双端队列是否为空。isFull()：查看双端队列是否满了。示例：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);                    // 曾经满了，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
 

 

提醒：所有值的范畴为 [1, 1000]
    操作次数的范畴为 [1, 1000]
    请不要应用内置的双端队列库。起源：力扣（LeetCode）链接：https://leetcode-cn.com/problems/design-circular-deque
著作权归领扣网络所有。商业转载请分割官网受权，非商业转载请注明出处。

题解

class MyCircularDeque {int[] data;
    int size;

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {data = new int[k];
    }
    
    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {if(isFull()){return false;}
        for(int i=size-1; i>=0; i--){data[i+1] = data[i];
        }
        data[0] = value;
        size++;
        return true;
    }
    
    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    public boolean insertLast(int value) {if(isFull()){return false;}
        data[size] = value;
        size++;
        return true;
    }
    
    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {if(isEmpty()){return false;}
        data[0] = 0;
        for(int i=0; i<size-1; i++){data[i]=data[i+1];
        }
        size--;
        return true;
    }
    
    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {if(isEmpty()){return false;}
        data[size-1] = 0;
        size--;
        return true;
    }
    
    /** Get the front item from the deque. */
    public int getFront() {return size == 0 ? -1 : data[0];
    }
    
    /** Get the last item from the deque. */
    public int getRear() {return size == 0 ? -1 : data[size-1];
    }
    
    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {return size == 0;}
    
    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {return size == data.length;}
}

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque obj = new MyCircularDeque(k);
 * boolean param_1 = obj.insertFront(value);
 * boolean param_2 = obj.insertLast(value);
 * boolean param_3 = obj.deleteFront();
 * boolean param_4 = obj.deleteLast();
 * int param_5 = obj.getFront();
 * int param_6 = obj.getRear();
 * boolean param_7 = obj.isEmpty();
 * boolean param_8 = obj.isFull();
 */

小结

这里采纳数组实现，insert 操作之前都要先判断是否满了，delete 操作之前都要先判断是否空了，对于 insertFront 及 deleteFront 都要设置数组元素的拷贝。

doc

• 设计循环双端队列