【CodeVS 1199】【NOIP 2012】开车旅行

http://codevs.cn/problem/1199/

主要思想是倍增，对于第一个回答从后往前扫，依次插入平衡树中。

我写的splay，比较繁琐。

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#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int N = 100003;
int in() {
    int k = 0, fh = 1; char c = getchar();
    for(; c < '0' || c > '9'; c = getchar())
        if (c == '-') fh = -1;
    for(; c >= '0' && c <= '9'; c = getchar())
        k = (k << 3) + (k << 1) + c - '0';
    return k * fh;
}
 
int h[N], n, m, nxt_a[N], nxt_b[N], f[N][18], sum_a[N][18], sum_b[N][18];
 
struct Splay {
    struct node {
        node *ch[2], *fa;
        int id, num;
        bool pl() {return fa->ch[1] == this;}
        void setc(node *r, bool c) {ch[c] = r; r->fa = this;}
    } *root, *null;
    void init() {
        null = new node;
        null->id = null->num = 0;
        null->ch[0] = null->ch[1] = null->fa = null;
        root = null;
    }
    void printall(node *r) {
        if (r == null) return;
        printall(r->ch[0]);
        printf("%d ", r->num);
        printall(r->ch[1]);
    }
    void rotate(node *r) {
        node *f = r->fa;
        bool c = r->pl();
        if (f != root) f->fa->setc(r, f->pl());
        else root = r, r->fa = null;
        f->setc(r->ch[!c], c);
        r->setc(f, !c);
    }
    void splay(node *r) {
        for(; r->fa != null; rotate(r))
            if (r->fa->fa != null) rotate(r->fa->pl() == r->pl() ? r->fa : r);
    }
    struct data {
        int del, h, id;
        bool operator < (const data &A) const {
            return (del == A.del ? h < A.h : del < A.del);
        }
    } a[5];
    node *getl(int num, int to) {
        node *r = root->ch[0];
        if (r == null) {a[to] = (data) {0x7fffffff, 0, 0}; return r;}
        while (r->ch[1] != null) r = r->ch[1];
        a[to] = (data) {abs(num - r->num), r->num, r->id};
        return r;
    }
    node *getr(int num, int to) {
        node *r = root->ch[1];
        if (r == null) {a[to] = (data) {0x7fffffff, 0, 0}; return r;}
        while (r->ch[0] != null) r = r->ch[0];
        a[to] = (data) {abs(num - r->num), r->num, r->id};
        return r;
    }
    void mk_nxt(int &back_1, int &back_2, int id, int num) {
        node *r = root;
        if (r == null) {
            root = new node;
            root->id = id; root->num = num;
            root->ch[0] = root->ch[1] = root->fa = null;
            back_1 = back_2 = 0;
            return;
        }
        bool c;
        while (true) {
            if (r->num > num) c = 0;
            else c = 1;
            if (r->ch[c] == null) {
                r->ch[c] = new node;
                r->ch[c]->fa = r;
                r = r->ch[c];
                r->id = id; r->num = num;
                r->ch[0] = r->ch[1] = null;
                splay(r);
                node *ll = getl(num, 0), *rr = getr(num, 1);
                if (ll != null) {splay(ll); getl(num, 2);} else a[2] = (data) {0x7fffffff, 0, 0};
                if (rr != null) {splay(rr); getr(num, 3);} else a[3] = (data) {0x7fffffff, 0, 0};
                sort(a, a + 4);
                if (a[1].id != 0) {
                    back_1 = a[1].id; back_2 = a[0].id;
                } else if (a[0].id != 0) {
                    back_1 = 0; back_2 = a[0].id;
                } else {
                    back_1 = 0; back_2 = 0;
                }
                return;
            } else r = r->ch[c];
        }
    }
} T;
 
void cal(int &a, int &b, int s, int x) {
    a = b = 0;
    for(int i = 17; i >= 0; --i)
        if (f[s][i] && sum_a[s][i] + sum_b[s][i] <= x) {
            a += sum_a[s][i]; b += sum_b[s][i];
            x -= sum_a[s][i]; x -= sum_b[s][i];
            s = f[s][i];
        }
    if (sum_a[s][0] <= x && nxt_a[s])
        a += sum_a[s][0];
}
 
int main() {
    T.init();
    n = in();
    for(int i = 1; i <= n; ++i) h[i] = in();
    for(int i = n; i >= 1; --i)  T.mk_nxt(nxt_a[i], nxt_b[i], i, h[i]);
     
    for(int i = 1; i <= n; ++i) {
        if (nxt_a[i]) sum_a[i][0] = abs(h[nxt_a[i]] - h[i]);
        if (nxt_b[nxt_a[i]]) {
            sum_b[i][0] = abs(h[nxt_b[nxt_a[i]]] - h[nxt_a[i]]);
            f[i][0] = nxt_b[nxt_a[i]];
        }
    }
    for(int j = 1; j <= 17; ++j)
        for(int i = 1; i <= n; ++i)
            if (f[f[i][j - 1]][j - 1]) {
                f[i][j] = f[f[i][j - 1]][j - 1];
                sum_a[i][j] = sum_a[i][j - 1] + sum_a[f[i][j - 1]][j - 1];
                sum_b[i][j] = sum_b[i][j - 1] + sum_b[f[i][j - 1]][j - 1];
            }
     
    int a, b, s, x, ans = 0; double ans_num = -1.0, now;
    x = in();
    for(int i = 1; i <= n; ++i) {
        cal(a, b, i, x);
        if (b != 0) now = 1.0 * a / b;
        else now = -1.0;
        if (ans_num == -1.0 || (ans_num != -1.0 && now != -1.0 && now <= ans_num))
            if (fabs(ans_num - now) < 1e-12) {
                if (h[i] > h[ans]) ans = i;
            } else ans_num = now, ans = i;
    }
    printf("%d\n", ans);
     
    m = in(); int i = 0;
    while (m--) {
        ++i;
        s = in(); x = in();
        cal(a, b, s, x);
        printf("%d %d\n", a, b);
    }
     
    return 0;
}