Submission #1038044

#	Time	Username	Problem	Language	Result	Execution time	Memory
1038044		karok	Race (IOI11_race)	C++17	9 / 100	288 ms	17084 KiB

race

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

#define int long long

struct Edges {
    int target, weight;
};

const int MAXN = 200000 + 200;
const int MAXK = 1000000 + 200;

int n, k;
vector<vector<Edges>> adj(MAXN);
int tree_size[MAXN] = {};
bool is_removed[MAXN] = {};

int get_tree_size(int cur_vertex, int parent = -1) {
    int &res = tree_size[cur_vertex];
    res = 1;
    for (auto [v, w] : adj[cur_vertex]) {
        if (v == parent || is_removed[v])continue;
            continue;
        res += get_tree_size(v, cur_vertex);
    }
    return res;
}

int get_centroid(int cur_vertex, int n, int parent = -1) {
    for (auto [v, w] : adj[cur_vertex]) {
        if (parent == v || is_removed[v])
            continue;
        if (tree_size[v] * 2 > n)
            return get_centroid(v, n, cur_vertex);
    }
    return cur_vertex;
}

int dfs(int cur_v,int cur_length, int total_ans, map<int,int> &past_lengths, int parent = -1){
    int res = INT_MAX;
    if(past_lengths.count( k - cur_length )) {
        res = total_ans  + past_lengths[k - cur_length];
    }
    for(auto [v, w]: adj[cur_v]){
        if(v == parent || is_removed[v]) continue;
        res = min(dfs(v, w + cur_length, total_ans + 1, past_lengths, cur_v), res);
    }
    if(past_lengths.count(cur_length)) past_lengths[cur_length] = min(past_lengths[cur_length], res);
    else past_lengths[cur_length] = res;
    return res;
}

int centroid_dfs(int cur_v) {
    int centroid = get_centroid(cur_v, get_tree_size(cur_v));
    int res;
    {
        map<int,int> lengths;
        lengths[0] = 0;
        res = dfs(centroid, 0, 0, lengths);
    }
    is_removed[centroid] = true;
    for(auto [u, w]: adj[centroid]) {
        if(is_removed[u])continue;
        res = min(centroid_dfs(u), res);
    }
    return res;
}

#undef int
int best_path(int a, int b, int h[][2] ,int l[] ) {
    n = a; k= b;
    for(int i =0;i < n - 1;i++) {
        adj[h[i][0]].push_back( Edges{h[i][1], l[i]} );
        adj[h[i][1]].push_back( Edges{h[i][0], l[i]} );
    }
    int ans = centroid_dfs(0);
    if(ans == INT_MAX) return -1;
    else return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57