POJ 1442 Black Box [Treap]

Description

Algorithm

Code

#include <iostream>
#include <cstdlib>
#include <cstdio>
using namespace std;
struct Node {
Node *ch[2]; //左右子树 0左1右
int r; //优先级
int v; //值
int s; //子树
Node(int v) : v(v) {
ch[0] = ch[1] = NULL;
r = rand();
s = 1;
}
int cmp(int x) {
if (x == v) return -1;
return x < v ? 0 : 1;
}
void maintain() {
s = 1;
if (ch[0] != NULL) s += ch[0]->s;
if (ch[1] != NULL) s += ch[1]->s;
}
};

void rotate(Node* &o, bool d)
{
Node *k = o->ch[!d];
o->ch[!d] = k->ch[d];
k->ch[d] = o;
o->maintain();
k->maintain();
o = k;
}
void insert(Node *&o, int x) //在 o 节点插入值为 x的节点
{
if (o == NULL) {
o = new Node(x);
} else {
bool d = x > (o->v);
insert(o->ch[d], x);
if (o->ch[d]->r > o->r) rotate(o, !d);
}
o->maintain();
}
void remove(Node * &o, int x)
{
int d = o->cmp(x);
if (d == -1) {
Node *u = o;
if (o -> ch[0] != NULL && o->ch[1] != NULL) {
bool d2 = o->ch[0]->r < o->ch[1]->r;
rotate(o, d2);
remove(o->ch[d2], x);
} else {
if (o->ch[0] == NULL) {
o = o->ch[1];
} else {
o = o->ch[0];
delete u;
}
}
} else {
remove(o->ch[d], x);
if (o != NULL) {
o->maintain();
}
}
}
int kth(Node *o, int k)
{
if (o == NULL || k <= 0 || k > o->s) return 0;
int s = o->ch[0] == NULL ? 0 : o->ch[0]->s;
if (k == s + 1) {
return o->v;
} else {
if(k <= s) {
return kth(o->ch[0], k);
} else {
return kth(o->ch[1], k-s-1);
}
}
}
int n, m;
const int MAXM = 30000 + 9;
const int MAXN = MAXM;
int a[MAXM];
int u[MAXN];
void solve()
{
for (int i = 0; i < m; i++) {
scanf("%d", &a[i]);
}
for (int i = 0; i < n; i++) {
scanf("%d", &u[i]);
}
int j = 0;
Node *treap = NULL;
for (int i = 0; i < n; i++) {
for (; j < u[i]; j++) {
insert(treap, a[j]);
}
printf("%d\n"<
968b
/span>, kth(treap, i + 1));
}
}
int main()
{
//freopen("in.txt", "r", stdin);
while (scanf("%d%d", &m, &n) != EOF) {
solve();
}
}