AT1984 [AGC001F] Wide Swap

https://www.luogu.com.cn/problem/AT1984

以下大量引用🐟大的blog

主要是这几个推论比较重要
用上面第一条就可以得到这题答案了

code:

#include<bits/stdc++.h>
#define N 1000050
using namespace std;
struct edge {
    int v, nxt;
} e[N << 1];
int p[N], eid, in[N];
void init() {
    memset(p, -1, sizeof p);
    eid = 0;
}
void insert(int u, int v) { //printf("%d --> %d\n", u, v);
    in[v] ++;
    e[eid].v = v;
    e[eid].nxt = p[u];
    p[u] = eid ++;
}
int ma[N << 2];
void update(int rt) {
    ma[rt] = max(ma[rt << 1], ma[rt << 1 | 1]);
}
void add(int rt, int l, int r, int x, int o) {
    if(l == r) {
        ma[rt] = o;
        return ;
    }
    int mid = (l + r) >> 1;
    if(x <= mid) add(rt << 1, l, mid, x, o);
    else add(rt << 1 | 1, mid + 1, r, x, o);
    update(rt);
}
int query(int rt, int l, int r, int L, int R) {
    if(L > R) return 0;
    if(L <= l && r <= R) return ma[rt];
    int mid = (l + r) >> 1, ret = 0;
    if(L <= mid) ret = query(rt << 1, l, mid, L, R);
    if(R > mid) ret = max(ret, query(rt << 1 | 1, mid + 1, r, L, R));
    return ret;
}
int n, k, a[N], b[N];
priority_queue<int> q;
int main() {
    init();
    scanf("%d%d", &n, &k); k --;
    for(int i = 1; i <= n; i ++) scanf("%d", &a[i]), b[a[i]] = i;

    for(int i = 1; i <= n; i ++) {
        int x = b[i], y = 0;
        y = query(1, 1, n, max(x - k, 1), x - 1);
        if(y) insert(x, b[y]);
        y = query(1, 1, n, x + 1, min(n, x + k));
        if(y) insert(x, b[y]);
        add(1, 1, n, x, i);
    }   

    for(int i = 1; i <= n; i ++) if(!in[i]) q.push(i);
    for(int i = n; i >= 1; i --) {
        int u = q.top(); q.pop();
        b[i] = u;
        for(int i = p[u]; i + 1; i = e[i].nxt) {
            int v = e[i].v;
            if((-- in[v]) == 0) q.push(v); 
        }
    }
    for(int i = 1; i <= n; i ++) a[b[i]] = i;
    for(int i = 1; i <= n; i ++) printf("%d\n", a[i]);
    return 0;
}