제출 #918514

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
918514		Boycl07	구슬과 끈 (APIO14_beads)	C++17	100 / 100	279 ms	42648 KiB

beads

#include <bits/stdc++.h>

using namespace std;

typedef long long 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 = 2e5 + 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];
int cnt[N], sum[N];
multiset<int> s[N];


vector<pii> g[N];

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


    for(pii e : g[u])
    {
        int v = e.fi, w = e.se;
        if(v == p) continue;
        int diff = dp[v][0] + w - max(dp[v][0], dp[v][1] + w);
        s[u].insert(diff);
    }
    if(cnt[u] >= 1) dp[u][1] = dp[u][0] + *(--s[u].end());
    else dp[u][1] = -INF;
}

void change(int u, int v, int w)
{
    int diff;
    --cnt[u];
    dp[u][0] -= max(dp[v][0], dp[v][1] + w);
    diff = dp[v][0] + w - max(dp[v][0], dp[v][1] + w);
    s[u].erase(s[u].find(diff));

    if(cnt[u] >= 1) dp[u][1] = dp[u][0] + *(--s[u].end());
    else dp[u][1] = -INF;


    ++cnt[v];
    dp[v][0] += max(dp[u][0], dp[u][1] + w);
    diff = dp[u][0] + w - max(dp[u][0], dp[u][1] + w);
    s[v].insert(diff);

    if(cnt[v] >= 1) dp[v][1] = dp[v][0] + *(--s[v].end());
    else dp[v][1] = -INF;

}

int res = 0;

void dfs_reroot(int u, int p)
{
    maximize(res, dp[u][0]);
    for(pii e : g[u])
    {
        int v = e.fi, w = e.se;
        if(v == p) continue;
        change(u, v, w);
        dfs_reroot(v, u);
        change(v, u, w);
    }
}

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});
    }
    dfs(1, 1);
    dfs_reroot(1, 1);
    cout << res;
}

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;
}

컴파일 시 표준 에러 (stderr) 메시지

beads.cpp: In function 'int main()':
beads.cpp:131:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  131 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:132:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  132 |         freopen(task"_slow.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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