leetcode雕蟲小技medium 641. Design Circular Deque

題幹： https://leetcode.com/problems/design-circular-deque/

這題跟622類似，算是它的進階版，要支持雙向的queue,大部分代碼我都複用622的方案，

唯獨要注意的一點是deleteLast和deleteFront要注意邊界條件，就是當刪完之後隊列爲空時，不要移動currentHead或者currentTail指針位置。

代碼如下：

package com.example.demo.leetcode;

import java.util.Arrays;

class MyCircularDeque {

    int[] content;

    int currentTail = 0;
    int currentHead = 0;

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {
        content = new int[k];
        Arrays.fill(content, -1);
    }

    private int previousPointer(int index){
        int p = index-1;
        if(p<0){
            p = p+content.length;
        }
        return p;
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {
        if(isFull()){
            return false;
        }
        if(content[currentHead]==-1){
            content[currentHead] = value;
            return true;
        }else{
            currentHead=previousPointer(currentHead);
            content[currentHead] = value;
            return true;
        }
    }

    private int nextPointer(int currentPointer){
        int p = currentPointer+1;
        if(p>content.length-1){
            p=p%content.length;
        }
        return p;
    }

    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    public boolean insertLast(int value) {
        if(isFull()){
            return false;
        }
        if(content[currentTail]==-1){
            content[currentTail] = value;
            return true;
        }else{
            currentTail = nextPointer(currentTail);
            content[currentTail]= value;
            return true;
        }
    }

    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if(isEmpty()){
            return false;
        }
        content[currentHead]=-1;
        if(content[nextPointer(currentHead)]!=-1){
            currentHead=nextPointer(currentHead);
        }
        return true;
    }

    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if(isEmpty()){
            return false;
        }
        content[currentTail] = -1;
        if(content[previousPointer(currentTail)]!=-1){
            currentTail = previousPointer(currentTail);
        }
        return true;
    }

    /** Get the front item from the deque. */
    public int getFront() {
        return content[currentHead];
    }

    /** Get the last item from the deque. */
    public int getRear() {
        return content[currentTail];
    }

    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {
        for(int i=0;i<content.length;i++){
            if(content[i]!=-1){
                return false;
            }
        }
        return true;
    }

    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {
        for(int i=0;i<content.length;i++){
            if(content[i]==-1){
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        MyCircularDeque obj = new MyCircularDeque(77);
        boolean param_1 = obj.insertFront(89);
        int param_2 = obj.getRear();
        boolean param_3 = obj.deleteLast();
        int param_4 = obj.getRear();
        boolean param_5 = obj.insertFront(19);
        boolean param_6 = obj.insertFront(23);
        boolean param_7 = obj.insertFront(23);
        boolean param_8 = obj.insertFront(82);
        boolean param_9 = obj.isFull();
        boolean param_10 = obj.insertFront(45);
        boolean param_11 = obj.isFull();
        int param_12 = obj.getRear();

        // expect 19
        System.out.println(param_12);
    }
}