题解P3165 [CQOI2014]排序机械臂

P3165 [CQOI2014]排序机械臂
一道Splay模板题,只不过需要注意一些细节

直接上代码

#include<iostream>
#include<cstdio>
#include<queue>
#include<algorithm>
using namespace std;
const int N = 1e5 + 5, INF = 0x3f3f3f3f;
typedef pair<int, int> PII;

struct tree
{
    int s[2], v, p, siz, lz;
    void init(int _v, int _p)
    {
        v = _v, p = _p, siz = 1;
    }
} tr[N];
int root, idx, hi[N];
PII poi[N];

bool cmp(PII a, PII b)
{
    if (a.first == b.first)
        return a.second < b.second;
    return a.first < b.first;
}//注意排序规则

void pushup(int p)
{
    tr[p].siz = tr[tr[p].s[0]].siz + tr[tr[p].s[1]].siz + 1;
}

void pushdown(int p)
{
    if (tr[p].lz)
    {
        tr[p].lz = 0;
        if (tr[p].s[0])
            tr[tr[p].s[0]].lz ^= 1;
        if (tr[p].s[1])
            tr[tr[p].s[1]].lz ^= 1;
        swap(tr[p].s[0], tr[p].s[1]);
    }
}

int build(int l, int r, int p)
{
    int mid = (l + r) >> 1;
    tr[mid].init(hi[mid], p), poi[mid] = {hi[mid], mid};
    if (l < mid)
        tr[mid].s[0] = build(l, mid - 1, mid);
    if (r > mid)
        tr[mid].s[1] = build(mid + 1, r, mid);
    pushup(mid);
    return mid;
}

void rotate(int x)
{
    int y = tr[x].p, z = tr[y].p;
    pushdown(y), pushdown(x);//下传标记
    int k = tr[y].s[1] == x;
    tr[z].s[tr[z].s[1] == y] = x, tr[x].p = z;
    tr[y].s[k] = tr[x].s[k ^ 1], tr[tr[x].s[k ^ 1]].p = y;
    tr[x].s[k ^ 1] = y, tr[y].p = x;
    pushup(y), pushup(x);
}

void splay(int x, int k)
{
    while (tr[x].p != k)
    {
        int y = tr[x].p, z = tr[y].p;
        pushdown(z), pushdown(y), pushdown(x);//提前下传标记
        if (z != k)
        { 
            if ((tr[y].s[1] == x) ^ (tr[z].s[1] == y))
                rotate(x);
            else
                rotate(y);
        }
        rotate(x);
    }
    if (!k)
        root = x;
}

int get_k(int k)
{
    int u = root;
    while (u)
    {
        pushdown(u);
        if (tr[tr[u].s[0]].siz >= k)
            u = tr[u].s[0];
        else if (tr[tr[u].s[0]].siz + 1 == k)
            return u;
        else
            k -= tr[tr[u].s[0]].siz + 1, u = tr[u].s[1];
    }
    return -1;
}

void reverse(int ll, int rr)
{
    int l = get_k(ll), r = get_k(rr + 2);
    splay(l, 0), splay(r, l);
    tr[tr[r].s[0]].lz ^= 1;
}

int main()
{
    int n;
    scanf("%d", &n);
    hi[1] = -INF, hi[n + 2] = INF;//下标从1开始
    for (int i = 2; i <= n + 1; i++)
        scanf("%d", &hi[i]);
    root = build(1, n + 2, 0);
    sort(poi + 1, poi + n + 3, cmp);
    for (int i = 2; i <= n + 1; i++)
    {
        int u = poi[i].second;
        splay(u, 0);
        int x = tr[tr[u].s[0]].siz + 1;
        printf("%d ", x - 1);
        reverse(i - 1, x - 1);
    }
    return 0;
}