(主席樹)P1801 黑匣子_NOI導刊2010提高
阿新 • • 發佈:2018-11-28
https://www.luogu.org/problemnew/show/P1801
題目可以用主席樹直接求解,ai <= 2000000000,需要離散化。
#include<bits/stdc++.h> using namespace std; const int maxn = 200000 + 10; struct in { int val, id; bool operator <(const in &x) const { return val < x.val; } } a[maxn]; int root[maxn], cnt, v[maxn]; struct seg { int lson, rson, num; } T[maxn * 40]; void update(int l, int r, int &rt, int &pre, int pos) { rt = ++cnt; T[rt] = T[pre]; T[rt].num++; if(l == r) return; int mid = l + r >> 1; if(pos <= mid) update(l, mid, T[rt].lson, T[pre].lson, pos); else update(mid + 1, r, T[rt].rson, T[pre].rson, pos); } int query(int l, int r, int pre, int now, int k) { if(l == r) return l; int mid = l + r >> 1; int num = T[T[now].lson].num - T[T[pre].lson].num; if(k <= num) return query(l, mid, T[pre].lson, T[now].lson, k); else return query(mid + 1, r, T[pre].rson, T[now].rson, k - num); } int main() { int n, m, x; cin >> n >> m; for(int i = 1; i <= n; i++) { cin >> a[i].val; a[i].id = i; } sort(a + 1, a + 1 + n); for(int i = 1; i <= n; i++) v[a[i].id] = i; root[0] = 0; for(int i = 1; i <= n; i++) update(1, n, root[i], root[i - 1], v[i]); for(int i = 1; i <= m; i++) { cin >> x; cout << a[query(1, n, root[0], root[x], i)].val << endl; } }