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法律研究实现优先级队列的 C++ 程序
队列作为 FIFO 实现，其中插入操作在端（后端）进行，删除操作在另一端（前端）进行。第一个进入元素首先被删除。
队列操作是
EnQueue (int data)：在后端进行插入
int DeQueue()：从前端进行删除
但是优先级队列不遵循先进先出，而是根据紧急性的基础每个元素都具有一个优先级。
具有相同优先级的项目根据先进先出服务基础进行处理。
具有更高优先级的项目在具有较低优先级的其他项目之前进行处理。
类描述
Begin class Priority_Queue has following functions: function insert() to insert items at priority queue with their priorities: 1) If queue is empty insert data from the left end of the queue. 2) If queue is having some nodes then insert the new node at the end of those nodes having priority same with the new node and also before all the nodes having priority lesser than the current priority of the new node. function del() to delete items from queue. If queue is completely empty, print underflow otherwise delete the front element and update front. End
示例
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;
struct n // node declaration {
int p;
int info;
struct n *l;
};
class Priority_Queue {
private:
//Declare a front pointer f and initialize it to NULL.
n *f;
public:
Priority_Queue() //constructor {
f = NULL;
}
void insert(int i, int p) {
n *t, *q;
t = new n;
t->info = i;
t->p = p;
if (f == NULL || p < f->p) {
t->l= f;
f = t;
} else {
q = f;
while (q->l != NULL && q->l->p <= p)
q = q->l;
t->l = q->l;
q->l = t;
}
}
void del() {
n *t;
if(f == NULL) //if queue is null
cout<<"Queue Underflow\n";
else {
t = f;
cout<<"Deleted item is: "<<t->info<<endl;
f = f->l;
free(t);
}
}
void show() //print queue {
n *ptr;
ptr = f;
if (f == NULL)
cout<<"Queue is empty\n";
else {
cout<<"Queue is :\n";
cout<<"Priority Item\n";
while(ptr != NULL) {
cout<<ptr->p<<" "<<ptr->info<<endl;
ptr = ptr->l;
}
}
}
};
int main() {
int c, i, p;
Priority_Queue pq;
Do//perform switch opeartion {
cout<<"1.Insert\n";
cout<<"2.Delete\n";
cout<<"3.Display\n";
cout<<"4.Exit\n";
cout<<"Enter your choice : ";
cin>>c;
switch(c) {
case 1:
cout<<"Input the item value to be added in the queue : ";
cin>>i;
cout<<"Enter its priority : ";
cin>>p;
pq.insert(i, p);
break;
case 2:
pq.del();
break;
case 3:
pq.show();
break;
case 4:
break;
default:
cout<<"Wrong choice\n";
}
}
while(c != 4);
return 0;
}输出
1.Insert 2.Delete 3.Display 4.Exit Enter your choice : 1 Input the item value to be added in the queue : 7 Enter its priority : 2 1.Insert 2.Delete 3.Display 4.Exit Enter your choice : 1 Input the item value to be added in the queue : 6 Enter its priority : 1 1.Insert 2.Delete 3.Display 4.Exit Enter your choice : 1 Input the item value to be added in the queue : 3 Enter its priority : 3 1.Insert 2.Delete 3.Display 4.Exit Enter your choice : 1 Input the item value to be added in the queue : 4 Enter its priority : 3 1.Insert 2.Delete 3.Display 4.Exit Enter your choice : 3 Queue is : Priority Item 1 6 2 7 3 3 3 4 1.Insert 2.Delete 3.Display 4.Exit Enter your choice : 4
更新时间：30-Jul-2019
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