poj2528

线段树，线段树一般是对连续的区块进行操作，每次给出相应的区块，但是本题给出海报覆盖的是区间，要把区间对应到区块上。虽然有些情况还不能处理，但是过了。

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;

#define maxn 20005

struct Interval
{
    int s, e;
}interval[maxn];

struct Node
{
    Node *pleft, *pright;
    int l, r;
    bool full;
}tree[maxn * 3];

int pos[maxn * 2], poscount, ncount;

void buildtree(Node *proot, int l, int r)
{
    proot->l = l;
    proot->r = r;
    if (l == r)
        return;
    int mid = (l + r) / 2;
    ncount++;
    proot->pleft = tree + ncount;
    ncount++;
    proot->pright = tree + ncount;
    buildtree(proot->pleft, l, mid);
    buildtree(proot->pright, mid + 1, r);
}

bool paste(Node *proot, int l, int r)
{
    if (l == r)
        return false;
    if (proot->full)
        return false;
    if (proot->l == l && proot->r == r - 1)
    {
        proot->full = true;
        return true;
    }
    int mid = (proot->l + proot->r) / 2;
    bool ret;
    if (r <= mid + 1)
        ret = paste(proot->pleft, l, r);
    else if (l > mid)
        ret = paste(proot->pright, l, r);
    else
    {
        ret = paste(proot->pleft, l, mid + 1);
        ret = paste(proot->pright, mid + 1, r) || ret;
    }
    proot->full = proot->pleft->full && proot->pright->full;
    return ret;
}

int binarysearch(int a)
{
    int l = 0;
    int r = poscount - 1;
    while (l < r)
    {
        int mid = (l + r) / 2;
        if (pos[mid] >= a)
            r = mid;
        else
            l = mid + 1;
    }
    return l;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    int t;
    scanf("%d", &t);
    while (t--)
    {
        poscount = 0;
        ncount = 0;
        memset(tree, 0, sizeof(tree));
        int n;
        scanf("%d", &n);
        for (int i = 0; i < n; i++)
        {
            scanf("%d%d", &interval[i].s, &interval[i].e);
            pos[poscount++] = interval[i].s;
            pos[poscount++] = interval[i].e;
        }
        sort(pos, pos + poscount);
        poscount = unique(pos, pos + poscount) - pos;
        buildtree(tree, 0, poscount - 1);
        int ans = 0;
        for (int i = n - 1; i >= 0; i--)
        {
            int s = binarysearch(interval[i].s);
            int e = binarysearch(interval[i].e) + 1;
            if (paste(tree, s, e))
                ans++;
        }
        printf("%d\n", ans);
    }
    return 0;
}