POJ1442 Black Box 堆

用大根堆和小根堆分别存放前$i-1$大的元素前$k-i$小的元素。 将当前序列的元素压入最小堆，如果最小堆的最小数大于最大堆的最大数则进行交换，保证最大堆中的所有数小于最小堆。 因为$i$值每进行一次自增$1$，所以每次$get$操作后将小根堆顶弹出存入大根堆。

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<cctype>
#include<cstdlib>
#include<vector>
#include<queue>
#include<map>
#include<set>
#define ull unsigned long long
#define ll long long
#define R register int
using namespace std;
namespace Fread {
    static char B[<<],*S=B,*D=B;
    #define getchar() (S==D&&(D=(S=B)+fread(B,1,1<<15,stdin),S==D)?EOF:*S++)
    inline int g() {
        R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;
        do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;
    } inline bool isempty(const char& ch) {return ch<=||ch>=;}
    inline void gs(char* s) {register char ch; while(isempty(ch=getchar())); do *s++=ch; while(!isempty(ch=getchar()));}
}using Fread::g; using Fread::gs;
priority_queue<int> bq;
priority_queue<int,vector<int>,greater<int> > sq;
int a[];
int n,m;
signed main() {
#ifdef JACK
    freopen("NOIPAK++.in","r",stdin);
#endif
    n=g(),m=g(); for(R i=;i<=n;++i) a[i]=g();
    R k=; for(R i=;i<=m;++i) {
        R x=g(); while(k<=x) {
            sq.push(a[k]); if(bq.size()&&bq.top()>sq.top()) {
                R tmp=bq.top(); bq.pop(); sq.push(tmp);
                tmp=sq.top(); sq.pop(); bq.push(tmp);
            } ++k;
        } printf("%d\n",sq.top());
        R tmp=sq.top(); sq.pop(); bq.push(tmp);
    }
}

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2019.06.13