poj 1442 Black Boxes（treap）求第k大数的treap模板

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依次加入n元素，给出m个询问 m<=n
第i个询问代表前q[i]里面第i个小的数是多少

#include <cstdio>#include <cstring>#include <ctime>#include <iostream>#include <algorithm>#include <cstdlib>#include <cmath>#include <utility>#include <vector>#include <queue>#include <map>#include <set>#define max(x,y) ((x)>(y)?(x):(y))#define min(x,y) ((x)>(y)?(y):(x))#define INF 0x3f3f3f3f#define MAXN 30005using namespace std;int cnt=1,rt=0;int n,m,a[MAXN],u[MAXN];struct Tree{    int key,size,pri,son[2];    void set(int x,int y,int z)    {        key=x;        pri=y;        size=z;        son[0]=son[1]=0;    }}T[MAXN];void rotate(int p,int &x){    int y=T[x].son[!p];    T[x].size=T[x].size-T[y].size+T[T[y].son[p]].size;    T[x].son[!p]=T[y].son[p];    T[y].size=T[y].size-T[T[y].son[p]].size+T[x].size;    T[y].son[p]=x;    x=y;}void ins(int key,int &x){    if(x==0)    {        T[x=cnt++].set(key,rand(),1);    }    else    {        T[x].size++;        int p=key<T[x].key;        ins(key,T[x].son[!p]);        if(T[x].pri<T[T[x].son[!p]].pri)            rotate(p,x);    }}int find(int p,int &x){    if(p==T[T[x].son[0]].size+1)        return T[x].key;    if(p>T[T[x].son[0]].size+1)        find(p-T[T[x].son[0]].size-1,T[x].son[1]);    else find(p,T[x].son[0]);}int main(){    scanf("%d%d",&n,&m);    for(int i=0;i<n;i++)        scanf("%d",&a[i]);    for(int i=1;i<=m;i++)    {        scanf("%d",&u[i]);        for(int j=u[i-1];j<u[i];j++)            ins(a[j],rt);        printf("%d\n",find(i,rt) );    }}

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