正题

题目链接:https://jzoj.net/senior/#contest/show/3008/0

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题目大意

一个队列要求支持

1. 队尾压入一个数
2. 队首弹出一个数
3. 队列里所有数取反
4. 求最大值

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解题思路

开$4$个堆，存正数最大值最小值，负数最大值最小值，取反时打标记即可。

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$code$

#pragma GCC optimize(2)
%:pragma GCC optimize(3)
%:pragma GCC optimize("Ofast")
%:pragma GCC optimize("inline")
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
struct node{int pos,val;
};
bool operator<(node x,node y)
{return x.val<y.val;}
struct node2{int pos,val;
};
bool operator<(node2 x,node2 y)
{return x.val>y.val;}
priority_queue<node> q1,q2;
priority_queue<node2> p1,p2;
int T,z,zero,tail,head,q[2010000];
int main()
{scanf("%d",&T);z=0;head=1;while(T--){char op[8];int x;scanf("%s",op);if(op[1]=='U'){scanf("%d",&x);if(!x) zero++,q[++tail]=0;else if((x>0)^z) q[++tail]=1,q1.push((node){tail,abs(x)}),p1.push((node2){tail,abs(x)});else if((x<0)^z) q[++tail]=-1,q2.push((node){tail,abs(x)}),p2.push((node2){tail,abs(x)});;}if(head>tail) continue;if(op[1]=='O'){if(!q[head]) zero--;head++;}if(op[1]=='I') z^=1;if(op[1]=='A'){while(!q1.empty()&&q1.top().pos<head) q1.pop();while(!q2.empty()&&q2.top().pos<head) q2.pop();while(!p1.empty()&&p1.top().pos<head) p1.pop();while(!p2.empty()&&p2.top().pos<head) p2.pop();if(!z){if(!q1.empty()) printf("%d\n",q1.top().val);else if(zero) printf("0\n");else if(!p2.empty()) printf("%d\n",-p2.top().val);}else{if(!q2.empty()) printf("%d\n",q2.top().val);else if(zero) printf("0\n");else if(!p1.empty()) printf("%d\n",-p1.top().val);}}}return 0;
}