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*4],lsum[N*4],rsum[N*4],cover[N*4],n,m;
void push_up(int k,int l,int r){
    int mid=l+r>>1;
    sum[k]=max(max(sum[k*2],sum[k*2+1]),rsum[k*2]+lsum[k*2+1]);
    lsum[k]=lsum[k*2];
    if(lsum[k*2]==mid-l+1) lsum[k]+=lsum[k*2+1];
    rsum[k]=rsum[k*2+1];
    if(rsum[k*2+1]==r-mid) rsum[k]+=rsum[k*2];
}
void push_down(int k,int l,int r){
    if(!cover[k]) return;
    int mid=l+r>>1;
    if(cover[k]==-1){
        lsum[k*2]=rsum[k*2]=sum[k*2]=0;
        lsum[k*2+1]=rsum[k*2+1]=sum[k*2+1]=0;
        cover[k*2]=cover[k*2+1]=-1;
    }
    else {
        lsum[k*2]=rsum[k*2]=sum[k*2]=mid-l+1;
        lsum[k*2+1]=rsum[k*2+1]=sum[k*2+1]=r-mid;
        cover[k*2]=cover[k*2+1]=1;
    }
    cover[k]=0;
}
void build(int l,int r,int k){
    if(l==r){
        cover[k]=0;
        lsum[k]=rsum[k]=sum[k]=1;
        return;
    }
    int mid=l+r>>1;
    build(l,mid,k*2);
    build(mid+1,r,k*2+1);
    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>>1;
    if(sum[k*2]>=x)return query(l,mid,k*2,x);
    else if(rsum[k*2]+lsum[k*2+1]>=x) return mid-rsum[k*2]+1;
    else return query(mid+1,r,k*2+1,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==-1?0:r-l+1;
        return;
    }
    push_down(k,l,r);
    int mid=l+r>>1;
    if(x<=mid) change(l,mid,k*2,c,x,y);
    if(y>mid) change(mid+1,r,k*2+1,c,x,y);
    push_up(k,l,r);
}
int main(){
    scanf("%d%d",&n,&m);
    build(1,n,1);
    for(int i=1;i<=m;i++){
        int opt,x,y;scanf("%d",&opt);
        if(opt==1){
            scanf("%d",&x);
            if(sum[1]<x){
                printf("0
");
                continue;
            }
            int p=query(1,n,1,x);
            printf("%d
",p);
            change(1,n,1,-1,p,p+x-1);
        }
        else {
            scanf("%d%d",&x,&y);
            change(1,n,1,1,x,x+y-1);
        }
    }
    return 0;
}