Submission #1073785

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073785		andrewp	Dreaming (IOI13_dreaming)	C++14	100 / 100	822 ms	18464 KiB

dreaming

//Dedicated to my love, ivaziva 
#include <bits/stdc++.h> 
#include "dreaming.h"
using namespace std; 

using pii = pair<int, int>;
using ll = int64_t;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define dbg(x) cerr << #x << ": " << x << '\n';

constexpr int mxN = 1e5 + 20;
vector<pii> g[mxN]; 
int par[mxN], dist[mxN], current_root = 0;     
bool vis[mxN]; 

void dfs(int x, int p, int& tr) {   
    if (dist[x] > dist[tr]) {
        tr = x;
    }
    if (p == -1) {
        dist[x] = 0;
    }
    par[x] = p;   
    vis[x] = true;  
    for (auto ptr: g[x]) {
        if (ptr.first != p) {  
            dist[ptr.first] = dist[x] + ptr.second;
            dfs(ptr.first, x, tr);  
        }
    }
}   

int travelTime(int N, int M, int L, int* A, int* B, int* T) {
    for (int i = 0; i < M; i++) {
        g[A[i]].push_back({B[i], T[i]});
        g[B[i]].push_back({A[i], T[i]});
    }  
    for (int i = 0; i < N; i++) {
        vis[i] = false; 
        dist[i] = 0;
    }
    vector<int> vv;
    int ans = 0; 
    for (int i = 0; i < N; i++) {
        if (!vis[i]) { 
            int root = i;
            current_root = i;
            dfs(i, -1, root);   
            int diamend = i;
            dfs(root, -1, diamend);
            int distance = dist[diamend]; 
            ans = max(ans, distance); 
            for (int ptr = diamend; ptr != -1; ptr = par[ptr]) {
                dbg(ptr);
                distance = min(distance, max(dist[ptr], dist[diamend] - dist[ptr]));
            }
            vv.push_back(distance); 
            dbg(distance);
        }       
    }      
    sort(rall(vv));
    if (vv.size() == 1) {
        return max(ans, vv[0]);
    } else if (vv.size() == 2) {
        return max(ans, vv[0] + vv[1] + L);
    }
    ans = max(ans, vv[0] + vv[1] + L);
    ans = max(ans, vv[1] + vv[2] + 2 * L);
    return ans;
}

/*int32_t main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    cout.tie(nullptr); cerr.tie(nullptr);

    int n, m, l;
    cin >> n >> m >> l;
    int a[m], b[m], t[m];
    for (int i = 0; i < m; i++) {
        cin >> a[i] >> b[i] >> t[i];
    }
    int ans = travelTime(n, m, l, a, b, t); 
    cout << ans << '\n';
    return 0;
}*/
/*
12 8 2
0 8 4
8 2 2
2 7 4
5 11 3
5 1 7
1 3 1
1 9 5
10 6 3 
*/

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