Submission #1241845

#	Time	Username	Problem	Language	Result	Execution time	Memory
1241845		nibert	Tree (IOI24_tree)	C++20	0 / 100	2094 ms	27448 KiB

tree

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int MAXN = 200005;

int N;
vector<int> tree[MAXN];
int weight[MAXN];
bool isLeaf[MAXN];
int leafCount[MAXN];

vector<pair<ll, ll>> segments; // a[t] * L + b[t] * R

void dfs_mark_leaves_and_count(int u) {
    isLeaf[u] = true;
    leafCount[u] = 0;
    for (int v : tree[u]) {
        isLeaf[u] = false;
        dfs_mark_leaves_and_count(v);
        leafCount[u] += leafCount[v];
    }
    if (isLeaf[u]) leafCount[u] = 1;
}

// Recursive decomposition
void decompose(int u, ll mulA, ll mulB) {
    int k = leafCount[u];
    if (isLeaf[u]) {
        segments.push_back({mulA * 1, mulB * 0}); // cost = L * W[u]
        return;
    }

    segments.push_back({mulA * k, mulB * (-1)}); // (kL - R) * W[u]

    for (int v : tree[u]) {
        decompose(v, mulA, mulB);
    }
}

void init(vector<int> P, vector<int> W) {
    N = P.size();
    for (int i = 0; i < N; ++i) {
        tree[i].clear();
        isLeaf[i] = false;
    }

    for (int i = 1; i < N; ++i) {
        tree[P[i]].push_back(i);
    }

    for (int i = 0; i < N; ++i) weight[i] = W[i];

    dfs_mark_leaves_and_count(0);

    segments.clear();
    decompose(0, 1, 1); // initial multipliers for L and R

    // Multiply weight at the segment origin
    for (auto& seg : segments) {
        seg.first *= weight[0];
        seg.second *= weight[0];
    }
}

ll query(int L, int R) {
    ll res = 0;
    for (auto& seg : segments) {
        res += seg.first * L + seg.second * R;
    }
    return res;
}

• Subtask 0: 0 / 0
• Subtask 1: 0 / 10
• Subtask 2: 0 / 13
• Subtask 3: 0 / 18
• Subtask 4: 0 / 7
• Subtask 5: 0 / 11
• Subtask 6: 0 / 22
• Subtask 7: 0 / 19