Submission #918510

#	Time	Username	Problem	Language	Result	Execution time	Memory
918510		Boycl07	Beads and wires (APIO14_beads)	C++17	28 / 100	1039 ms	1116 KiB

beads

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define int ll
#define rep(i, n) for(int i = 1; i <= n; ++i)
#define forn(i, l, r) for(int i = l; i <= r; ++i)
#define ford(i, r, l) for(int i = r; i >= l; --i)
#define FOR(i, n) for(int i = 0; i < n; ++i)
#define fi first
#define se second
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define endl "\n"
#define task "beads"
#define sz(a) int(a.size())
#define C(x, y) make_pair(x, y)
#define all(a) (a).begin(), (a).end()
#define bit(i, mask) (mask >> i & 1)

template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }

inline int readInt()       {char c;while(c=getchar(),c!='-'&&(c<'0'||c>'9'));bool sign=(c=='-');if(sign)c=getchar();int n=c-'0';while(c=getchar(),c>='0'&&c<='9')n=10*n+c-'0';return(!sign)?n:-n;}
inline ll readLong()       {char c;while(c=getchar(),c!='-'&&(c<'0'||c>'9'));bool sign=(c=='-');if(sign)c=getchar();ll  n=c-'0';while(c=getchar(),c>='0'&&c<='9')n=10*n+c-'0';return(!sign)?n:-n;}
inline string readString() {char c;while(c=getchar(),c==' '||c=='\n'||c=='\t');string s({c});while(c=getchar(),c!=EOF&&c!=' '&&c!='\n'&&c!='\t')s+=c;return s;}


const int N = 1e4 + 4;
const int M = 3e5 + 3;
const int K = 22;
const int INF = 1e9 + 3;
const ll LINF = 1e18;

int n;

int dp[N][2];

vector<pii> g[N];

int dfs(int u, int p, bool c)
{
    int &res = dp[u][c];

    if(res != -1) return res;
    res = -INF;

    int sum = 0;
    for(pii e : g[u])
    {
        int v = e.fi, w = e.se;
        if(v == p) continue;
        sum += max(dfs(v, u, 0), dfs(v, u, 1) + w);
    }

    int Max1 = -INF, Max2 = -INF, cnt = 0;
    for(pii e : g[u])
    {
        int v = e.fi, w = e.se;
        if(v == p) continue;
        ++cnt;
        int diff = dfs(v, u, 0) + w - max(dfs(v, u, 0), dfs(v, u, 1) + w);
        if(diff > Max1) Max2 = Max1, Max1 = diff;
        else maximize(Max2, diff);
    }
    if(c == 0) maximize(res, sum);
    if(cnt >= 1 && c == 1) maximize(res, sum + Max1);
    return res;
}

void solve()
{
    cin >> n;
    rep(i, n - 1)
    {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].pb({v, w});
        g[v].pb({u, w});
    }
    int res = 0;
    rep(i, n)
    {
        memset(dp, -1, sizeof dp);

        maximize(res, dfs(i, i, 0));
    }
    cout << res << endl;
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int TC = 1;

    if(fopen(task".inp", "r"))
    {
        freopen(task".inp", "r", stdin);
        freopen(task"_slow.out", "w", stdout);
    }


    while(TC--)
    {
        solve();
        cout << endl;
    }

    return 0;
}

Compilation message (stderr)

beads.cpp: In function 'int main()':
beads.cpp:103:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  103 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:104:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  104 |         freopen(task"_slow.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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