HDU-3667 Hotel 线段树 经典空间合并

http://poj.org/problem?id=3667

经典线段树，不解释了。

代码如下：

#include <cstdlib>
#include <cstring>
#include <cstdio> 
#include <algorithm>
#define MAXN 50000 
using namespace std;

struct
{
    int l, r;
    int lmax, rmax, max, cover;
}seg[MAXN*4];

void build(int f, int l, int r)
{
    int mid = l+r >> 1;
    seg[f].l = l, seg[f].r = r;
    seg[f].lmax = seg[f].rmax = seg[f].max = r-l+1;
    seg[f].cover = 0;
    if (r > l)
    {
        build(f<<1, l, mid);
        build(f<<1|1, mid+1, r);
    }
}

void up(int f)
{
    seg[f].lmax = seg[f<<1].lmax;
    seg[f].rmax = seg[f<<1|1].rmax;
    if (seg[f<<1].cover == 0)
        seg[f].lmax += seg[f<<1|1].lmax;
    if (seg[f<<1|1].cover == 0)
        seg[f].rmax += seg[f<<1].rmax;
    seg[f].max = max(seg[f<<1].max, seg[f<<1|1].max);
    seg[f].max = max(seg[f].max, seg[f<<1].rmax+seg[f<<1|1].lmax);
    if (seg[f<<1].cover == seg[f<<1|1].cover)
        seg[f].cover = seg[f<<1].cover;
    else
        seg[f].cover = -1;
}

void modify(int f, int l, int r, int val)
{
    int mid = seg[f].l+seg[f].r >> 1;
    if (seg[f].l == l && seg[f].r == r)
    {
        seg[f].cover = val;
        if (val == 0)
            seg[f].lmax = seg[f].rmax = seg[f].max = r-l+1;
        else
            seg[f].lmax = seg[f].rmax = seg[f].max = 0;
    }
    else if (seg[f].r > seg[f].l)
    { 
        if (seg[f].cover == 0)
        {
            seg[f<<1].cover = seg[f<<1|1].cover = 0;
            seg[f<<1].lmax = seg[f<<1].rmax = seg[f<<1].max = seg[f<<1].r-seg[f<<1].l+1;
            seg[f<<1|1].lmax = seg[f<<1|1].rmax = seg[f<<1|1].max = seg[f<<1|1].r-seg[f<<1|1].l+1;
            seg[f].cover = -1;
        }
        else if (seg[f].cover == 1)
        {
            seg[f<<1].cover = seg[f<<1|1].cover = 1;
            seg[f<<1].lmax = seg[f<<1].rmax = seg[f<<1].max = 0;
            seg[f<<1|1].lmax = seg[f<<1|1].rmax = seg[f<<1|1].max = 0;
            seg[f].cover = -1;
        }
        if (r <= mid)
            modify(f<<1, l, r, val);
        else if (l > mid)
            modify(f<<1|1, l, r, val);
        else
        {
            modify(f<<1, l, mid, val);
            modify(f<<1|1, mid+1, r, val);
        }
        up(f);
    }
}

int query(int f, int size)
{
    if (seg[f].max < size)
        return 0;
    else if (seg[f].lmax >= size)
        return seg[f].l;
    else if (seg[f<<1].max >= size)
        return query(f<<1, size);
    else if (seg[f<<1].rmax+seg[f<<1|1].lmax >= size)
        return seg[f<<1].r-seg[f<<1].rmax+1;
    else
        return query(f<<1|1, size);
}

int main()
{
    int N, M, op, size, s, e, pos;
    while (scanf("%d %d", &N, &M) == 2)
    {
        build(1, 1, N);
        while (M--)
        {
            scanf("%d", &op);
            if (op == 1)
            {
                scanf("%d", &size);
                pos = query(1, size); 
                printf("%d\n", pos);
                if (pos != 0)  // 执行占用命令
                    modify(1, pos, pos+size-1, 1);
            }
            else
            {
                scanf("%d %d", &s, &e);
                modify(1, s, s+e-1, 0);
            }
        }
    }
    return 0;
}