Tietoverkko

input/code.cpp: In function 'void set_io(std::__cxx11::string)':
input/code.cpp:16:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen((filename + ".in").c_str(), "r", stdin);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
input/code.cpp:17:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen((filename + ".out").c_str(), "w", stdout);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define fi first
#define se second
#define sz size
#define rsz resize

void set_io(string filename = "") {
    ios::sync_with_stdio(0);
	cin.tie(0);

    if (filename != "") {
        freopen((filename + ".in").c_str(), "r", stdin);
        freopen((filename + ".out").c_str(), "w", stdout);
    }
}

int LOG = 0;
vector<vector<pair<int,int>>> adj;
vector<int> depth;
vector<vector<int>> anc, bw;

void dfs(int a = 0, int l = -1, int d = 1) {
    for (auto n : adj[a]) {
        if (n.fi == l) continue;

        depth[n.fi] = d;
        anc[n.fi][0] = a;
        bw[n.fi][0] = n.se;

        for (int i = 1; i < LOG; i++) {
            anc[n.fi][i] = anc[anc[n.fi][i - 1]][i - 1];
            bw[n.fi][i] = min(bw[n.fi][i - 1], bw[anc[n.fi][i - 1]][i - 1]);
        }

        dfs(n.fi, a, d + 1);
    }
}

int getbw(int a, int b) {
    int ans = INT_MAX;

    if (depth[a] > depth[b]) swap(a, b);
    if (depth[a] < depth[b]) {
        int diff = depth[b] - depth[a];
        for (int i = LOG - 1; i >= 0; i--) {
            if (diff & (1 << i)) {
                if (bw[b][i]) ans = min(ans, bw[b][i]);
                b = anc[b][i];
            }
        }
    }

    if (a == b) return ans;

    for (int i = LOG - 1; i >= 0; i--) {
        if (anc[a][i] != anc[b][i]) {
            ans = min({ans, bw[a][i], bw[b][i]});
            a = anc[a][i];
            b = anc[b][i];
        }
    }

    return min({ans, bw[a][0], bw[b][0]});
}

int main() {
    set_io("");

    int n; cin >> n;
    adj.rsz(n); depth.rsz(n); 

    for (int i = 0; i < n-1; i++) {
        int a, b, x; cin >> a >> b >> x;
        adj[a-1].pb({b-1, x});
        adj[b-1].pb({a-1, x});
    }

    while (1 << (LOG + 1) <= n) LOG++;

    bw = anc = vector<vector<int>>(n, vector<int>(LOG));

    dfs();

    unsigned long long ans = 0;
    for (int i = 0; i < n; i++) for (int j = i + 1; j < n; j++) ans += getbw(i, j);

    cout << ans << endl;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: TIME LIMIT EXCEEDED