跟線段樹求區間最值一樣每個節點維護左邊開始的最大連續空房間數、右邊開始的最大連續空房間數、這個區間內的最大連續空房間數

#include <iostream>
#include <cstdio>
using namespace std;
int n, m, opt, uu, vv;
struct SGT{
    int lma[200005], rma[200005], sum[200005], tag[200005];
    //sum means there are how many empty rooms
    //tag==2 means these room should be clear, 1 means not
 

    void pushUp(int o, int l, int r, int lson, int rson, int mid){
        if(sum[lson]==mid-l+1)  lma[o] = mid - l + 1 + lma[rson];
        else    lma[o] = lma[lson];
        if(sum[rson]==r-mid)    rma[o] = r - mid + rma[lson];
        else    rma[o] = rma[rson];
        sum[o] = max(rma[lson] + lma[rson], max(sum[lson], sum[rson]));
    }
    void
 
 pushDown(int o, int l, int r, int lson, int rson, int mid){
        tag[lson] = tag[rson] = tag[o];
        sum[lson] = lma[lson] = rma[lson] = (mid - l + 1) * (tag[o] - 1);
        sum[rson] = lma[rson] = rma[rson] = (r - mid) * (tag[o] - 1);
        tag[o] = 0;
    }
    void build(int o, int l, int
 
 r){
        if(l==r)    lma[o] = rma[o] = sum[o] = 1;
        else{
            int mid=(l+r)>>1;
            int lson=o<<1;
            int rson=lson|1;
            if(l<=mid)  build(lson, l, mid);
            if(mid<r)   build(rson, mid+1, r);
            pushUp(o, l, r, lson, rson, mid);
        }
    }
    int query(int o, int l, int r, int x){
        if(l==r)    return l;
        else{
            int mid=(l+r)>>1;
            int lson=o<<1;
            int rson=lson|1;
            if(tag[o])  pushDown(o, l, r, lson, rson, mid);
            if(sum[lson]>=x)    return query(lson, l, mid, x);
            else if(rma[lson]+lma[rson]>=x) return mid-rma[lson]+1;
            else    return query(rson, mid+1, r, x);
        }
    }
    void modify(int o, int l, int r, int x, int y, int k){
        if(l>=x && r<=y){
            sum[o] = lma[o] = rma[o] = (r - l + 1) * (k - 1);
            tag[o] = k;
        }
        else{
            int mid=(l+r)>>1;
            int lson=o<<1;
            int rson=lson|1;
            if(tag[o])  pushDown(o, l, r, lson, rson, mid);
            if(x<=mid)  modify(lson, l, mid, x, y, k);
            if(mid<y)   modify(rson, mid+1, r, x, y, k);
            pushUp(o, l, r, lson, rson, mid);
        }
    }
}sgt;
int main(){
    cin>>n>>m;
    sgt.build(1, 1, n);
    while(m--){
        scanf("%d", &opt);
        if(opt==1){
            scanf("%d", &uu);
            if(sgt.sum[1]<uu)   printf("0\n");
            else{
                int ans=sgt.query(1, 1, n, uu);
                printf("%d\n", ans);
                sgt.modify(1, 1, n, ans, ans+uu-1, 1);
            }       
        }
        else{
            scanf("%d %d", &uu, &vv);
            sgt.modify(1, 1, n, uu, uu+vv-1, 2);
        }
    }
    return 0;
}

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