#include<stdio.h>
#include<iostream>
using namespace std;
int i = 0;
void push_head(int *a, int d) {//头部插入元素
for(int j = i-1; j >= 0; j--) a[j+1] = a[j];//遍历往后推一个
a[0] = d;
i++;
}
void push_end(int *a, int d) { a[i++] = d; }
void pop_head(int *a) {
if(a[i-1] == 0) cout << "队列已空\n";
else {
for(int j = 0; j <= i; j++) a[j] = a[j+1];//遍历往前推一个
i--;
}
}
void pop_end(int *a) {
if(a[i-1] == 0) cout << "队列已空\n";
else {
a[i-1] = 0;
i--;
}
}
void show(int *a) {
cout << "该队列的元素";
for(int i = 0; i < 1000; i++) {
if(a[i] != 0)
printf("a[%d] = %d ", i, a[i]);
}
cout << endl;
}
int main() {
int d, a[10000];
string s;
while(cin >> s) {
if(s == "push_end") { cin >> d; push_end(a, d); show(a); } //末尾增加一个d
if(s == "push_head") { cin >> d; push_head(a, d); show(a); }//头部增加一个d
if(s == "pop_head") { pop_head(a); show(a); }//删除头部元素
if(s == "pop_end") { pop_end(a); show(a); }//删除尾部元素
}
}
