Submission #581024

#	Time	Username	Problem	Language	Result	Execution time	Memory
581024		tranxuanbach	Dreaming (IOI13_dreaming)	C++17	18 / 100	51 ms	14412 KiB

dreaming

#ifndef FEXT

#include "dreaming.h"

#endif

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

#define endl '\n'
#define fi first
#define se second
#define For(i, l, r) for (auto i = l; i < r; i++)
#define ForE(i, l, r) for (auto i = l; i <= r; i++)
#define FordE(i, l, r) for (auto i = l; i >= r; i--)
#define Fora(v, a) for (auto v: a)
#define bend(a) a.begin(), a.end()
#define isz(a) ((signed)a.size())

using ll = long long;
using ld = long double;
using pii = pair <int, int>;
using vi = vector <int>;
using vpii = vector <pair <int, int>>;
using vvi = vector <vector <int>>;

const int N = 1e5 + 5;

int n, m, l;
vpii adj[N];

bool vis[N];

pii dfs_farthest(int u, int p){
    vis[u] = 1;
    pii ans = make_pair(0, u);
    Fora(edge, adj[u]){
        int v, w; tie(v, w) = edge;
        if (v == p){
            continue;
        }
        pii tans = dfs_farthest(v, u);
        tans.fi += w;
        ans = max(ans, tans);
    }
    return ans;
}

int h1[N], h2[N];

void dfs_h(int u, int p, int h[]){
    Fora(edge, adj[u]){
        int v, w; tie(v, w) = edge;
        if (v == p){
            continue;
        }
        h[v] = h[u] + w;
        dfs_h(v, u, h);
    }
}

void dfs_r(int u, int p, int &r){
    r = min(r, max(h1[u], h2[u]));
    Fora(edge, adj[u]){
        int v, w; tie(v, w) = edge;
        if (v == p){
            continue;
        }
        dfs_r(v, u, r);
    }
}

int travelTime(int _n, int _m, int _l, int _a[], int _b[], int _t[]){
    n = _n; m = _m; l = _l;
    For(i, 0, m){
        int u = _a[i], v = _b[i], w = _t[i];
        adj[u].emplace_back(v, w);
        adj[v].emplace_back(u, w);
    }

    int ans = 0, ans1 = -1, ans2 = -1, ans3 = -2;

    ForE(u, 1, n){
        if (vis[u]){
            continue;
        }
        int d1 = dfs_farthest(u, u).se;
        int d, d2; tie(d, d2) = dfs_farthest(d1, d1);
        ans = max(ans, d);
        dfs_h(d1, d1, h1);
        dfs_h(d2, d2, h2);

        int r = INT_MAX;
        dfs_r(u, u, r);

        if (ans1 < r){
            ans3 = ans2; ans2 = ans1; ans1 = r;
        }
        else if (ans2 < r){
            ans3 = ans2; ans2 = r;
        }
        else if (ans3 < r){
            ans3 = r;
        }
    }

    if (ans1 == -1){
        return ans;
    }
    if (ans2 == -1){
        return ans;
    }
    if (ans3 == -1){
        ans = max(ans, ans2 + l + ans1);
    }
    else{
        ans = max(ans, ans2 + l + max(ans1, ans3 + l));
    }
    return ans;
}

#ifdef FEXT

#define fail(s, x...) do { \
        fprintf(stderr, s "\n", ## x); \
        exit(1); \
    } while(0)

#define MAX_N 100000

static int A[MAX_N];
static int B[MAX_N];
static int T[MAX_N];

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    freopen("KEK.inp", "r", stdin);
    freopen("KEK.out", "w", stdout);
    int N, M, L, i;

    cin >> N >> M >> L;
    for (i = 0; i < M; i++)
        cin >> A[i] >> B[i] >> T[i];

    int answer = travelTime(N, M, L, A, B, T);
    cout << answer << endl;

    return 0;
}

#endif

/*
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INPUT:                                            |
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OUTPUT:                                           |
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*/

• Subtask 1: 0 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 18 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23