2021 MetaCamp程序设计大赛线上资格赛 7-2 心情故事【主席树】

#include<cstdio>
#include<cstring>
#include<algorithm>
#define mid (l+r)/2
using namespace std;
typedef long long ll;

const int N = 200010;
int n, q, m, cnt = 0;
int a[N], b[N], T[N];
int sum[N<<5], L[N<<5], R[N<<5];

inline int build(int l, int r)
{
    int rt = ++ cnt;
    sum[rt] = 0;
    if (l < r){
        L[rt] = build(l, mid);
        R[rt] = build(mid+1, r);
    }
    return rt;
}

inline int update(int pre, int l, int r, int x)
{
    int rt = ++ cnt;
    L[rt] = L[pre]; R[rt] = R[pre]; sum[rt] = sum[pre]+1;
    if (l < r){
        if (x <= mid) L[rt] = update(L[pre], l, mid, x);
        else R[rt] = update(R[pre], mid+1, r, x);
    }
    return rt;
}

inline int query(int u, int v, int l, int r, int k)
{
    if (l >= r) return l;
    int x = sum[L[v]] - sum[L[u]];
    if (x >= k) return query(L[u], L[v], l, mid, k);
    else return query(R[u], R[v], mid+1, r, k-x);
}

int main()
{
	
    while(scanf("%d%d", &n, &q)!=EOF){
		for (int i = 1; i <= n; i ++){
			scanf("%d", &a[i]);
			b[i] = a[i];
		}
		sort(b+1, b+1+n);
		m = unique(b+1, b+1+n)-b-1;
		T[0] = build(1, m);
		for (int i = 1; i <= n; i ++){
			int t = lower_bound(b+1, b+1+m, a[i])-b;
			T[i] = update(T[i-1], 1, m, t);
		}
		for(int i=1;i<=n-q+1;i++){
			int x=i, y=i+q-1, z=q-3+1;
			int t = query(T[x-1], T[y], 1, m, z);
			printf("%d ", b[t]);
		}
		printf("\n");
	}
    return 0;
}