「HNOI2004」宠物收养场

「HNOI2004」宠物收养场

传送门
对宠物和人各维护一棵平衡树，每次 \(\text{split}\) 的时候记得判一下子树是否为空，然后模拟就好了。
参考代码：

#include <algorithm>
#include <cstdlib>
#include <cstdio>
#define rg register
#define file(x) freopen(x".in", "r", stdin), freopen(x".out", "w", stdout)
using namespace std;
template < class T > inline void read(T & s) {
    s = 0; int f = 0; char c = getchar();
    while ('0' > c || c > '9') f |= c == '-', c = getchar();
    while ('0' <= c && c <= '9') s = s * 10 + c - 48, c = getchar();
    s = f ? -s : s;
}

const int _ = 8e4 + 5, mod = 1e6;

int n, rt1, rt2, tot, siz[_], val[_], pri[_], ch[2][_];

inline int Newnode(int v)
{ return siz[++tot] = 1, val[tot] = v, pri[tot] = rand(), tot; }

inline void pushup(int p) { siz[p] = siz[ch[0][p]] + siz[ch[1][p]] + 1; }

inline int merge(int x, int y) {
    if (!x || !y) return x + y;
    if (pri[x] > pri[y])
        return ch[1][x] = merge(ch[1][x], y), pushup(x), x;
    else
        return ch[0][y] = merge(x, ch[0][y]), pushup(y), y;
}

inline void split(int p, int v, int& x, int& y) {
    if (!p) { x = y = 0; return ; }
    if (val[p] <= v)
        return x = p, split(ch[1][p], v, ch[1][x], y), pushup(p);
    else
        return y = p, split(ch[0][p], v, x, ch[0][y]), pushup(p);
}

inline int kth(int p, int k) {
    if (siz[ch[0][p]] + 1 > k) return kth(ch[0][p], k);
    if (siz[ch[0][p]] + 1 == k) return val[p];
    if (siz[ch[0][p]] + 1 < k) return kth(ch[1][p], k - siz[ch[0][p]] - 1);
}

inline void insert(int& rt, int item) {
    int a, b;
    split(rt, item, a, b);
    rt = merge(a, merge(Newnode(item), b));
}

inline void erase(int& rt, int item) {
    int a, b, c;
    split(rt, item, a, c);
    split(a, item - 1, a, b);
    b = merge(ch[0][b], ch[1][b]);
    rt = merge(a, merge(b, c));
}

inline int match(int& rt, int item) {
    int a, b, x, y, res;
    split(rt, item, a, b);
    if (a == 0 && b != 0) res = kth(b, 1);
    if (a != 0 && b == 0) res = kth(a, siz[a]);
    if (a != 0 && b != 0)
        x = kth(a, siz[a]), y = kth(b, 1), res = item - x <= y - item ? x : y;
    rt = merge(a, b);
    return res;
}

int main() {
#ifndef ONLINE_JUDGE
    file("cpp");
#endif
    read(n);
    int ans = 0;
    for (rg int a, b, x, i = 1; i <= n; ++i) {
        read(a), read(b);
        if (a == 0) {
            if (rt2 == 0) insert(rt1, b);
            else x = match(rt2, b), erase(rt2, x), ans = (ans + abs(x - b)) % mod;
        } else {
            if (rt1 == 0) insert(rt2, b);
            else x = match(rt1, b), erase(rt1, x), ans = (ans + abs(x - b)) % mod;
        }
    }
    printf("%d\n", ans);
    return 0;
}