洛谷P2824 [HEOI2016/TJOI2016]排序
二分答案,将原数组中小于二分值的置0,大于等于的置1,则区间排序问题则可变为区间赋值问题
线段树维护区间和,记cnt为[l,r]区间的1的个数,区间升序排序[l,r]可以转为对[r-cnt+1,r]区间值变为1,[l,r-cnt]区间值变为0,区间降序同理
若所求pos的值为1,说明经过一轮排序后该点的值是大于等于二分的答案的,可知单调性
#include <bits/stdc++.h>
#include <ext/pb_ds/priority_queue.hpp>
//#pragma GCC optimize("O2")
using namespace std;
using namespace __gnu_pbds;
#define Pair pair<LL,LL>
#define Combine Pair, greater<Pair>, pairing_heap_tag
#define LL long long
#define ll long long
#define ULL unsigned long long
#define ls rt<<1
#define rs rt<<1|1
#define one first
#define two second
#define MS 1000009
#define INF 1e18
#define DBINF 1e100
#define Pi acos(-1.0)
#define eps 1e-9
#define mod 99999997
LL n,m;
LL mid;
LL a[MS];
struct node{
LL op,l,r;
}cp[MS];
LL p[MS<<2];
LL la[MS<<2];
void push_up(int rt){
p[rt] = p[ls] + p[rs];
}
void push_down(int rt,int l,int r){
if(la[rt] != -1){
int m = l+r>>1;
p[ls] = (m-l+1)*la[rt];
p[rs] = (r-m)*la[rt];
la[ls] = la[rt];
la[rs] = la[rt];
la[rt] = -1;
}
}
void build(int l,int r,int rt){
la[rt] = -1;
if(l == r){
if(a[l] < mid) p[rt] = 0;
else p[rt] = 1;
return;
}
int m = l+r>>1;
build(l,m,ls);
build(m+1,r,rs);
push_up(rt);
}
void update(int L,int R,int l,int r,int rt,LL val){
if(L <= l && r <= R){
p[rt] = (r-l+1)*val;
la[rt] = val;
return;
}
int m = l+r>>1;
push_down(rt,l,r);
if(m >= L) update(L,R,l,m,ls,val);
if(m < R) update(L,R,m+1,r,rs,val);
push_up(rt);
}
LL get_sum(int L,int R,int l,int r,int rt){
if(L <= l && r <= R){
return p[rt];
}
int m = l+r>>1;
push_down(rt,l,r);
LL ans = 0;
if(m >= L) ans += get_sum(L,R,l,m,ls);
if(m < R) ans += get_sum(L,R,m+1,r,rs);
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin >> n >> m;
for(int i=1;i<=n;i++){
cin >> a[i];
}
for(int i=1;i<=m;i++){
cin >> cp[i].op >> cp[i].l >> cp[i].r;
}
LL pos,ans;
cin >> pos;
LL l = 1 ,r = n;
while(l<=r){
mid = l+r>>1;
build(1,n,1);
for(int i=1;i<=m;i++){
LL cnt = get_sum(cp[i].l,cp[i].r,1,n,1);
if(!cnt || cnt == cp[i].r-cp[i].l+1) continue;
if(!cp[i].op){
update(cp[i].l,cp[i].r-cnt,1,n,1,0);
update(cp[i].r-cnt+1,cp[i].r,1,n,1,1);
}
else{
update(cp[i].l,cp[i].l+cnt-1,1,n,1,1);
update(cp[i].l+cnt,cp[i].r,1,n,1,0);
}
}
LL tar = get_sum(pos,pos,1,n,1);
if(tar) ans = mid ,l = mid+1;
else r = mid-1;
}
cout << ans << endl;
return 0;
}