c_cpp 使用数组实现线性队列

Posted 2021-05-14

#include <bits/stdc++.h>
#define MAX_SIZE 10
using namespace std;

// #Queue #BasicProblem
//Slots of array are reused in this procedure

bool isFull(int frontIndex,int backIndex){
    if(backIndex-frontIndex+1==MAX_SIZE){  //size of array is (last_i-first_i)+1
        return true;
    }else{
        return false;
    }
}
bool isEmpty(int frontIndex,int backIndex){
    if(backIndex-frontIndex+1==0){
        return true;
    }else{
        return false;
    }
}
bool Enq(int Q[],int push,int &frontIndex,int &backIndex){
    if(isFull(frontIndex,backIndex)==true){
        return false;
    }else{
        backIndex++;
        Q[backIndex]=push;
        return true;
    }
}
bool Deq(int Q[],int &frontIndex,int &backIndex,int &removed){
    if(isEmpty(frontIndex,backIndex)==true){
        return false;
    }else{
        removed=Q[frontIndex];
        for(int i=frontIndex;i<backIndex;i++){
            Q[i]=Q[i+1]; //moving elements to the left
        }
        backIndex--;	// fot the left shift
        return true;
    }
}

int main() {
    cout<<"Instructions: \n";
    cout<<"Type add to Enqueue"<<endl;
    cout<<"Type del to Dequeue"<<endl;
    cout<<"Type front to check front element"<<endl;
    cout<<"Type exit to stop using the Queue"<<endl;
    int Q[MAX_SIZE];
    int frontIndex=0; //front index always stays 0 as the elements are all moved left for every dequeue
    									//so is this variable necessary?
    int backIndex=-1; // initializing an empty Queue
    int removed; // variable to access the element dequeued
    while(1){
        string instruction;
        cout<<"Instruction: ";
        cin>>instruction;
        if(instruction=="exit"){
            break;
        }else if(instruction=="add"){
            cout<<"Enter the element top be enqueued"<<endl;
            int push; //element to be enqueued
            cin>>push;
            if(Enq(Q,push,frontIndex,backIndex)==true){
                cout<<"Element "<<Q[backIndex]<<" successfully enqueued"<<endl;
            }else{
                cout<<"ERROR: Queue is already full!"<<endl;
            }
        }else if(instruction=="del"){
            if(Deq(Q,frontIndex,backIndex,removed)==true){
                cout<<"Element "<<removed<<" successfully Dequeued"<<endl;
                if(isEmpty(frontIndex,backIndex)==false){
                        cout<<"Front Element is:"<<Q[frontIndex]<<endl;
                }else{
                    cout<<"Queue is now Empty!"<<endl;
                }
            }else{
                cout<<"ERROR : Queue is empty!"<<endl;
            }
        }else if(instruction=="front"){
            if(isEmpty(frontIndex,backIndex)==false){
                cout<<"Front Element is:"<<Q[frontIndex]<<endl;
            }else{
                cout<<"Queue is now Empty!"<<endl;
            }
        }else{
            cout<<"ERROR : Unknown operation! Please try again"<<endl;
        }
    }
    return 0;
}