PKU 3667 - Hotel (线段树 + 区间合并 + 区间覆盖)

思路

学习了区间修改的线段树。。还要好好消化

代码

#include <cstdio>
#include <stack>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <functional>
#include <cstring>
#include <algorithm>
#include <cctype>
#include <ctime>
#include <cstdlib>
#include <fstream>
#include <string>
#include <sstream>
#include <map>
#include <cmath>
#define LL long long
#define SZ(x) (int)x.size()
#define Lowbit(x) ((x) & (-x))
#define MP(a, b) make_pair(a, b)
#define MS(arr, num) memset(arr, num, sizeof(arr))
#define PB push_back
#define F first
#define S second
#define ROP freopen("input.txt", "r", stdin);
#define MID(a, b) (a + ((b - a) >> 1))
#define LC rt << 1, l, mid
#define RC rt << 1|1, mid + 1, r
#define LRT rt << 1
#define RRT rt << 1|1
#define BitCount(x) __builtin_popcount(x)
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
using namespace std;
const int MAXN = 51000 + 10;
const int MOD = 20071027;
 
typedef pair<int, int> pii;
typedef vector<int>::iterator viti;
typedef vector<pii>::iterator vitii;
 
struct SEGTREE
{
    int lmax, rmax, max, cover;
}segt[MAXN << 2];
 
void PushUp(int rt, int m)
{
    segt[rt].lmax = segt[LRT].lmax; segt[rt].rmax = segt[RRT].rmax;
    if (segt[rt].lmax == (m - (m >> 1))) segt[rt].lmax += segt[RRT].lmax;
    if (segt[rt].rmax == (m >> 1)) segt[rt].rmax += segt[LRT].rmax;
    segt[rt].max = max(segt[LRT].rmax + segt[RRT].lmax, max(segt[LRT].max, segt[RRT].max));
}
 
void PushDown(int rt, int m)
{
    segt[LRT].lmax = segt[LRT].rmax = segt[LRT].max = (segt[rt].cover ? 0 : m - (m >> 1));
    segt[RRT].lmax = segt[RRT].rmax = segt[RRT].max = (segt[rt].cover ? 0 : (m >> 1));
    segt[LRT].cover = segt[RRT].cover = segt[rt].cover;
    segt[rt].cover = -1;
}
 
void Update(int rt, int l, int r, int L, int R, int type)
{
    if (L <= l && r <= R)
    {
        segt[rt].lmax = segt[rt].rmax = segt[rt].max = (type ? 0 : r - l + 1);
        segt[rt].cover = type;
        return;
    }
    if (segt[rt].cover != -1) PushDown(rt, r - l + 1);
    int mid = MID(l, r);
    if (L <= mid) Update(LC, L, R, type);
    if (R > mid) Update(RC, L, R, type);
    PushUp(rt, r - l + 1);
}
 
int Query(int rt, int l, int r, int val)
{
    if (l == r) return l;
    if (segt[rt].cover != -1) PushDown(rt, r - l + 1);
    int mid = MID(l, r);
    if (segt[LRT].max >= val) return Query(LC, val);
    else if (segt[LRT].rmax + segt[RRT].lmax >= val) return mid - segt[LRT].rmax + 1;
    else Query(RC, val);
}
 
void Build(int rt, int l, int r)
{
    segt[rt].lmax = segt[rt].rmax = segt[rt].max = r - l + 1;
    segt[rt].cover = -1;
    if (l == r) return;
    int mid = MID(l, r);
    Build(LC); Build(RC);
}
 
int main()
{
    //ROP;
    int ntot, n, i, j;
    scanf("%d%d", &ntot, &n);
    Build(1, 1, ntot);
    while (n--)
    {
        int k, a, b;
        scanf("%d", &k);
        if (k == 1)
        {
            scanf("%d", &a);
            if (segt[1].max < a) puts("0");
            else
            {
                int p = Query(1, 1, ntot, a);
                printf("%d\n", p);
                Update(1, 1, ntot, p, p + a - 1, 1);
            }
        }
        else
        {
            scanf("%d%d", &a, &b);
            Update(1, 1, ntot, a, a + b - 1, 0);
        }
    }
    return 0;
}

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