POJ 2104 K-th Number 主席树

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int MAXN = 1e5+5;

int N,M;
int A[MAXN];

int has[MAXN];
int htot;
int get(int x){
int tt = lower_bound(has,has+htot,x)-has;
return tt+1;
}
int show(int x){
return has[x-1];
}

struct Node{
int ls; int rs; int sum;
}tree[MAXN*30];
int root[MAXN];
int tot; int Ed;
int Build(int l,int r) {
int rt = tot++;
tree[rt].sum = 0;
if(l == r) return rt;
int m = (l+r) >>1;
tree[rt].ls = Build(l,m);
tree[rt].rs = Build(m+1,r);
return rt;
}
int Update(int pos,int num,int l,int r,int pre) {
int rt = tot++;
tree[rt] = tree[pre];
tree[rt].sum += num;
if(l == r) return rt;
int m = (l+r) >>1;
if(pos <= m) tree[rt].ls = Update(pos,num,l,m,tree[pre].ls);
else tree[rt].rs = Update(pos,num,m+1,r,tree[pre].rs);
return rt;
}

int Qans;
void Query(int num,int l,int r,int rt1,int rt2) {
if(l == r) {
Qans = r; return;
}
int m = (l + r) >>1;
int tt = tree[tree[rt2].ls].sum - tree[tree[rt1].ls].sum;
if(tt >= num) Query(num,l,m,tree[rt1].ls,tree[rt2].ls);
else Query(num-tt, m+1, r, tree[rt1].rs,tree[rt2].rs);
}
void Debug(int l,int r,int rt){
printf("%d %d %d\n",l,r,tree[rt].sum);
if(l == r) {
return;
}
int m = (l+r) >>1;
Debug(l,m,tree[rt].ls); Debug(m+1,r,tree[rt].rs);
}
int main(){
while(~scanf("%d %d",&N,&M)) {
htot = 0;
for(int i = 1; i <= N; ++i) { scanf("%d",&A[i]); has[htot ++] = A[i]; }
sort(has,has+htot);
htot = unique(has, has+htot) - has;
Ed = htot;

tot = 0; root[0] = Build(1,Ed);
for(int i = 1; i <= N; ++i) {
int tt = get(A[i]);
root[i] = Update(tt, 1, 1, Ed, root[i-1]);
}
//	Debug(1,Ed,root[5]); printf("\n");
//	for(int i = 1; i <= N; ++i) printf("%d ",root[i]); printf("\n");

for(int i = 1; i <= M; ++i) {
int a,b,c; scanf("%d %d %d",&a,&b,&c);
Query(c,1,Ed,root[a-1],root[b]);
printf("%d\n",show(Qans) );
}
}
return 0;
}