【USACO 2008FEB】 旅馆

【题目链接】

          点击打开链接

【算法】

          线段树

          对于一个节点，记录它从左端点延伸的最多的空房间的个数，从右端点延伸的最多的空房间个数，和该区间最多的连续

          空房间个数

【代码】

          

#include<bits/stdc++.h>
using namespace std;
#define MAXN 50010

int n,m,opt,pos,x,d;

struct SegmentTree
{
        struct Node
        {
                int l,r,lm,rm,mx,tag;
        } Tree[MAXN*4];
        inline void build(int index,int l,int r)
        {
                int mid;
                Tree[index].l = l;
                Tree[index].r = r;
                Tree[index].lm = Tree[index].rm = Tree[index].mx = r - l + 1;
                Tree[index].tag = -1;
                if (l == r) return;
                mid = (l + r) >> 1;
                build(index<<1,l,mid);
                build(index<<1|1,mid+1,r);
        }
        inline void pushdown(int index)
        {
                int ql = Tree[index].l,qr = Tree[index].r;
                int mid = (ql + qr) >> 1;
                if (ql == qr) return;
                if (Tree[index].tag == 0)
                {
                        Tree[index<<1].lm = Tree[index<<1].rm = Tree[index<<1].mx = mid - ql + 1;
                        Tree[index<<1|1].lm = Tree[index<<1|1].rm = Tree[index<<1|1].mx = qr - mid;
                        Tree[index<<1].tag = Tree[index<<1|1].tag = 0;
                        Tree[index].tag = -1;
                }
                if (Tree[index].tag == 1)
                {
                        Tree[index<<1].lm = Tree[index<<1].rm = Tree[index<<1].mx = 0;
                        Tree[index<<1|1].lm = Tree[index<<1|1].rm = Tree[index<<1|1].mx = 0;
                        Tree[index<<1].tag = Tree[index<<1|1].tag = 1;
                        Tree[index].tag = -1;
                }
        }
        inline void update(int index)
        {
                int ql = Tree[index].l,qr = Tree[index].r;
                int mid = (ql + qr) >> 1;
                if (Tree[index<<1].lm == mid - ql + 1) Tree[index].lm = Tree[index<<1].lm + Tree[index<<1|1].lm;
                else Tree[index].lm = Tree[index<<1].lm;
                if (Tree[index<<1|1].rm == qr - mid) Tree[index].rm = Tree[index<<1|1].rm + Tree[index<<1].rm;
                else Tree[index].rm = Tree[index<<1|1].rm;
                Tree[index].mx = max(max(Tree[index<<1].mx,Tree[index<<1|1].mx),Tree[index<<1].rm+Tree[index<<1|1].lm);
        }
        inline void modify(int index,int l,int r,int val)
        {
                int mid,ql,qr;
                if (Tree[index].l == l && Tree[index].r == r)
                {
                        Tree[index].lm = Tree[index].rm = Tree[index].mx = (val ^ 1) * (r - l + 1);
                        Tree[index].tag = val;
                } else
                {
                        pushdown(index);
                        ql = Tree[index].l;
                        qr = Tree[index].r;
                        mid = (ql + qr) >> 1;
                        if (mid >= r) modify(index<<1,l,r,val);
                        else if (mid + 1 <= l) modify(index<<1|1,l,r,val);
                        else 
                        {
                                modify(index<<1,l,mid,val);
                                modify(index<<1|1,mid+1,r,val);
                        }
                        update(index);
                }
        }
        inline int query_pos(int index,int d)
        {
                int mid,ql,qr;
                ql = Tree[index].l; qr = Tree[index].r;
                mid = (ql + qr) >> 1;
                if (ql == qr) return ql;
                pushdown(index);
                if (Tree[index<<1].mx >= d) return query_pos(index<<1,d);
                else if (Tree[index<<1].rm + Tree[index<<1|1].lm >= d) return mid - Tree[index<<1].rm + 1;
                else return query_pos(index<<1|1,d);
        }
        inline int query()
        {
                return Tree[1].mx;
        }
} T;

template <typename T> inline void read(T &x)
{
    int f = 1; x = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
    for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
    x *= f;
}
template <typename T> inline void write(T x)
{
    if (x < 0)
    {
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x/10);
    putchar(x%10+'0');
}
template <typename T> inline void writeln(T x)
{
    write(x);
    puts("");
}

int main() {
        
        read(n); read(m);
        T.build(1,1,n);
        while (m--)
        {
                read(opt);
                if (opt == 1)
                {
                        read(d);
                        if (T.query() < d) writeln(0);
                        else 
                        {
                                pos = T.query_pos(1,d);
                                writeln(pos);
                                T.modify(1,pos,pos+d-1,1);
                        }
                } else
                {
                        read(x); read(d);
                        T.modify(1,x,x+d-1,0);
                }
        }
        
        return 0;
    
}