题解:主席树裸题 查询第K小出现的下标
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <stack>
#include <queue>
#include <cmath>
#include <set>
#include <map>
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define link(x) for(edge *j=h[x];j;j=j->next)
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,r,l) for(int i=r;i>=l;i--)
const int MAXN=1e5+10;
const int NM=2e3+10;
const double eps=1e-8;
#define ll long long
using namespace std;
struct edge{int t;edge*next;}e[MAXN<<1],*h[MAXN],*o=e;
void add(int x,int y){o->t=y;o->next=h[x];h[x]=o++;}
ll read(){
ll x=0,f=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return x*f;
}
int p[MAXN],cnt,a[MAXN],fp[MAXN],num[MAXN],rt[MAXN];
vector<int>vec;
int pos[MAXN];
void dfs(int x,int fa){
p[x]=++cnt;fp[p[x]]=x;num[x]=1;
link(x){
if(j->t!=fa)dfs(j->t,x),num[x]+=num[j->t];
}
}
typedef struct node{
int l,r,sum;
}node;
node d[21*MAXN];
void update(int &x,int y,int l,int r,int t){
x=++cnt;d[x]=d[y];d[x].sum++;
if(l==r)return ;
int mid=(l+r)>>1;
if(t<=mid)update(d[x].l,d[y].l,l,mid,t);
else update(d[x].r,d[y].r,mid+1,r,t);
}
int ans;
void querty(int x,int y,int l,int r,int k){
if(l==r){ans=l;return ;}
int mid=(l+r)>>1;
int t=d[d[y].l].sum-d[d[x].l].sum;
if(k<=t)querty(d[x].l,d[y].l,l,mid,k);
else querty(d[x].r,d[y].r,mid+1,r,k-t);
}
int main(){
int n;n=read();
inc(i,1,n)a[i]=read(),vec.pb(a[i]);
sort(vec.begin(),vec.end());
int sz=unique(vec.begin(),vec.end())-vec.begin();
inc(i,1,n)a[i]=lower_bound(vec.begin(),vec.begin()+sz,a[i])-vec.begin()+1,pos[a[i]]=i;
int u,v;
inc(i,1,n-1)u=read(),v=read(),add(u,v),add(v,u);
dfs(1,0);
inc(i,1,n)update(rt[i],rt[i-1],1,sz,a[fp[i]]);
int m=read();
while(m--){
u=read();v=read();
querty(rt[p[u]-1],rt[p[u]+num[u]-1],1,sz,v);
printf("%d
",pos[ans]);
}
}
1803: Spoj1487 Query on a tree III
Time Limit: 1 Sec Memory Limit: 64 MBSubmit: 760 Solved: 329
[Submit][Status][Discuss]
Description
You are given a node-labeled rooted tree with n nodes. Define the query (x, k): Find the node whose label is k-th largest in the subtree of the node x. Assume no two nodes have the same labels.
Input
The first line contains one integer n (1 <= n <= 10^5). The next line contains n integers li (0 <= li <= 109) which denotes the label of the i-th node. Each line of the following n - 1 lines contains two integers u, v. They denote there is an edge between node u and node v. Node 1 is the root of the tree. The next line contains one integer m (1 <= m <= 10^4) which denotes the number of the queries. Each line of the next m contains two integers x, k. (k <= the total node number in the subtree of x)
Output
For each query (x, k), output the index of the node whose label is the k-th largest in the subtree of the node x.
Sample Input
5
1 3 5 2 7
1 2
2 3
1 4
3 5
4
2 3
4 1
3 2
3 2
1 3 5 2 7
1 2
2 3
1 4
3 5
4
2 3
4 1
3 2
3 2
Sample Output
5
4
5
5