HDU - 4366 Successor DFS序 + 分块暴力 or 线段树维护

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
#define inf (0x3f3f3f3f)
typedef long long int LL;

#include <iostream>
#include <sstream>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <string>
const int maxn = 50000 + 20;
struct edge {
    int u, v, next;
} e[maxn * 2];
int first[maxn], R[maxn], L[maxn], mx[maxn];
int magic;
struct node {
    int abliatly, loyalty ;
    bool operator < (const node &rhs) const {
        return abliatly < rhs.abliatly;
    }
} a[maxn], List[maxn], to_sort[maxn];
int get_id[1000000 + 20];
int n, num;
void add (int u, int v)
{
    ++num;
    e[num].u = u;
    e[num].v = v;
    e[num].next = first[u];
    first[u] = num;
}
bool book[maxn];
int index;
void dfs (int cur)
{
    L[cur] = index;
    for (int i = first[cur]; i; i = e[i].next) {
        if (book[e[i].v]) continue;
        book[e[i].v] = 1;
        ++index;
        List[index] = to_sort[index] = a[e[i].v];
        dfs (e[i].v);
    }
    R[cur] = index;
}
int find (int begin, int end, int val)
{
    int t = end;
    if (to_sort[end].abliatly < val) return -1; //不够它大
    if (to_sort[begin].abliatly > val) return mx[begin];//bigger
    while (begin <= end) {
        int mid = (begin + end) >> 1;
        if (to_sort[mid].abliatly > val) end = mid - 1;
        else begin = mid + 1;
    }
    if (begin > t) return -1;
    return mx[begin];
}
void work ()
{
    int Q;
    scanf ("%d%d", &n, &Q);
    magic = (int) sqrt (n * 1.0);
    for (int i = 1; i <= n - 1; ++i) {
        int fa, lo, ab;
        scanf ("%d%d%d", &fa, &lo, &ab);
        add (fa, i);
        a[i].abliatly = ab;
        a[i].loyalty = lo;
        get_id[lo] = i;
    }
    dfs (0); //dfs 构图
    for (int i = 0; i < n; i += magic) {
        int j = i + magic;
        if (j > n) break;
        sort (to_sort + i, to_sort + j);
        mx[j - 1] = to_sort[j - 1].loyalty;
        for (int k = j - 2; k >= i; --k) {
            mx[k] = mx[k + 1] > to_sort[k].loyalty ? mx[k + 1] : to_sort[k].loyalty;
        }
    }
    while (Q--) {
        int id;
        scanf ("%d", &id);
        int val = a[id].abliatly;
        int ans = -inf;
        int begin = L[id], end = R[id];
        for (int i = begin; i <= end;) {
            if (i % magic == 0 && i + magic - 1 <= end) {
                int t = find (i, i + magic - 1, val);
                ans = max (ans, t);
                i += magic;
            } else {
                if (List[i].abliatly > val && ans < List[i].loyalty) {
                    ans = List[i].loyalty;
                }
                ++i;
            }
        }
        printf ("%d\n", ans < 0 ? -1 : get_id[ans]);
    }
    return ;
}

int main ()
{
#ifdef local
    freopen("data.txt","r",stdin);
#endif
    int t;
    scanf ("%d", &t);
    a[0].abliatly = -1;
    a[0].loyalty = -1;
    List[0] = to_sort[0] = a[0];
    while (t--) {
        work ();
        memset (first, 0, sizeof first);
        memset (book, 0, sizeof book);
        num = 0;
        index = 0;
        memset (mx, 0, sizeof mx);
    }
    return 0;
}