Submission #997558

#	Time	Username	Problem	Language	Result	Execution time	Memory
997558		coolboy19521	Dreaming (IOI13_dreaming)	C++17	100 / 100	72 ms	25776 KiB

dreaming

#include "bits/stdc++.h"
#include "dreaming.h"

using namespace std;

const int sz = 1e5 + 5;

vector <vector <int>> aj[sz];

int f[sz], s[sz], c[sz];
bool us[sz];
int mn, cn;

void dfs1(int v, int p) {
    us[v] = true;

    for (auto& u : aj[v]) {
        if (u[0] == p) continue;
        dfs1(u[0], v);
        if (f[u[0]] + u[1] > f[v]) {
            s[v] = f[v];
            f[v] = f[u[0]] + u[1];
            c[v] = u[0];
        } else {
            s[v] = max(s[v], f[u[0]] + u[1]);
        }
    }
}

void dfs2(int v, int p) {
    if (f[v] < mn) {
        mn = f[v];
        cn = v;
    }

    for (auto& u : aj[v]) {
        if (u[0] == p) continue;
        if (c[v] == u[0]) {
            if (s[v] + u[1] > f[u[0]]) {
                s[u[0]] = f[u[0]];
                f[u[0]] = s[v] + u[1];
                c[u[0]] = v;
            } else {
                s[u[0]] = max(s[u[0]], s[v] + u[1]);
            }
        } else {
            s[u[0]] = f[u[0]];
            f[u[0]] = f[v] + u[1];
            c[u[0]] = v;
        }

        dfs2(u[0], v);
    }
}

void dfs3(int v, int p) {
    f[v] = s[v] = 0;

    for (auto& u : aj[v]) {
        if (u[0] == p) continue;
        dfs3(u[0], v);
        if (f[u[0]] + u[1] > f[v]) {
            s[v] = f[v];
            f[v] = f[u[0]] + u[1];
        } else {
            s[v] = max(s[v], f[u[0]] + u[1]);
        }
    }

    // cout << v << ' ' << f[v] << ' ' << s[v] << '\n';

    s[v] = f[v] + s[v];
    mn = max({mn, f[v], s[v]});
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    for (int i = 0; i < M; i ++) {
        aj[A[i]].push_back({B[i], T[i]});
        aj[B[i]].push_back({A[i], T[i]}); 
    }

    vector <vector <int>> rs;

    for (int i = 0; i < N; i ++) {
        if (!us[i]) {
            mn = INT_MAX;

            dfs1(i, 0);
            dfs2(i, 0);

            rs.push_back({mn, cn});
        }
    }

    sort(begin(rs), end(rs));

    int mx = rs.back()[1];

    for (int i = 0; i < (int) rs.size() - 1; i ++) {
        int cur = rs[i][1];
        aj[mx].push_back({cur, L});
        aj[cur].push_back({mx, L});
        // cout << "CONNECT " << mx << ' ' << cur << '\n';
    }

    mn = 0;
    dfs3(0, -1);

    return mn;
}

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