Submission #525181

#	Time	Username	Problem	Language	Result	Execution time	Memory
525181		XII	Beads and wires (APIO14_beads)	C++17	0 / 100	3 ms	5024 KiB

beads

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

using ll = long long;

#define fi first
#define se second
#define mp make_pair
#define eb emplace_back
#define ALL(x) (x).begin(), (x).end()

#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORU(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)

#define IOS cin.tie(0)->sync_with_stdio(false);
#define PROB "APIO14_beads"
void Fi(){
    if(fopen(PROB".inp", "r")){
        freopen(PROB".inp", "r", stdin);
        freopen(PROB".out", "w", stdout);
    }
}

const int N = 2e5 + 1;
const ll INF = 1e15;
int n;
ll dp[2][N];
using pi = pair<int, int>;
vector<pi> adj[N];

void dfs(int u, int p = -1){
    ll dif[2] = {-INF, -INF}, tot = 0;
    for(auto [w, v]: adj[u]) if(v != p){
        dfs(v, u);
        tot += max(dp[0][v], dp[1][v] + w);
        ll spcl = (dp[0][v] + w) - max(dp[0][v], dp[1][v] + w);
        if(spcl > dif[0]){
            dif[1] = dif[0];
            dif[0] = spcl;
        } else dif[1] = max(dif[1], spcl);
    }
    dp[0][u] = max(tot, tot + dif[0] + dif[1]);
    dp[1][u] = tot + dif[0];
}

int main(){
    IOS;
    Fi();
    cin >> n;
    FOR(i, 1, n){
        int u, v, w;
        cin >> u >> v >> w;
        adj[u].eb(w, v);
        adj[v].eb(w, u);
    }
    dfs(1);
    cout << dp[0][1];
    return 0;
}

Compilation message (stderr)

beads.cpp: In function 'void Fi()':
beads.cpp:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |         freopen(PROB".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:21:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |         freopen(PROB".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43