Hotel（poj 3667）

题意：询问区间最长连续空串

/*
  用线段树维护区间最长连续左空串和右空串
*/
#include<cstdio>
#include<iostream>
#define N 50010
using namespace std;
int sum[N*],lsum[N*],rsum[N*],cover[N*],n,m;
void push_up(int k,int l,int r){
    int mid=l+r>>;
    sum[k]=max(max(sum[k*],sum[k*+]),rsum[k*]+lsum[k*+]);
    lsum[k]=lsum[k*];
    if(lsum[k*]==mid-l+) lsum[k]+=lsum[k*+];
    rsum[k]=rsum[k*+];
    if(rsum[k*+]==r-mid) rsum[k]+=rsum[k*];
}
void push_down(int k,int l,int r){
    if(!cover[k]) return;
    int mid=l+r>>;
    if(cover[k]==-){
        lsum[k*]=rsum[k*]=sum[k*]=;
        lsum[k*+]=rsum[k*+]=sum[k*+]=;
        cover[k*]=cover[k*+]=-;
    }
    else {
        lsum[k*]=rsum[k*]=sum[k*]=mid-l+;
        lsum[k*+]=rsum[k*+]=sum[k*+]=r-mid;
        cover[k*]=cover[k*+]=;
    }
    cover[k]=;
}
void build(int l,int r,int k){
    if(l==r){
        cover[k]=;
        lsum[k]=rsum[k]=sum[k]=;
        return;
    }
    int mid=l+r>>;
    build(l,mid,k*);
    build(mid+,r,k*+);
    push_up(k,l,r);
}
int query(int l,int r,int k,int x){
    if(l==r)return l;
    push_down(k,l,r);
    int mid=l+r>>;
    if(sum[k*]>=x)return query(l,mid,k*,x);
    else if(rsum[k*]+lsum[k*+]>=x) return mid-rsum[k*]+;
    else return query(mid+,r,k*+,x);
}
void change(int l,int r,int k,int c,int x,int y){
    if(l>=x&&r<=y){
        cover[k]=c;
        lsum[k]=rsum[k]=sum[k]=c==-?:r-l+;
        return;
    }
    push_down(k,l,r);
    int mid=l+r>>;
    if(x<=mid) change(l,mid,k*,c,x,y);
    if(y>mid) change(mid+,r,k*+,c,x,y);
    push_up(k,l,r);
}
int main(){
    scanf("%d%d",&n,&m);
    build(,n,);
    for(int i=;i<=m;i++){
        int opt,x,y;scanf("%d",&opt);
        if(opt==){
            scanf("%d",&x);
            if(sum[]<x){
                printf("0\n");
                continue;
            }
            int p=query(,n,,x);
            printf("%d\n",p);
            change(,n,,-,p,p+x-);
        }
        else {
            scanf("%d%d",&x,&y);
            change(,n,,,x,x+y-);
        }
    }
    return ;
}