Submission #1073761

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073761		andrewp	Dreaming (IOI13_dreaming)	C++14	77 / 100	1068 ms	16328 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 dist1[mxN], dist2[mxN], par[mxN]; 
int dist3[mxN], dist4[mxN]; 
bool vis[mxN];
vector<int> vec, dijametar;
vector<pii> vv;

void dfs(int x, int p) {   
    vis[x] = true;   
    vec.push_back(x);  
    for (auto ptr: g[x]) {
        if (ptr.first != p) {  
            dist1[ptr.first] = dist1[x] + ptr.second;
            dfs(ptr.first, x);  
        }
    }
}  
void dfs2(int x, int p) {   
    par[x] = p;
    for (auto ptr: g[x]) {
        if (ptr.first != p) {  
            dist2[ptr.first] = dist2[x] + ptr.second;
            dfs2(ptr.first, x);  
        }
    }
}  

void dfs3(int x, int p) {
    for (auto ptr: g[x]) {
        if (ptr.first != p) {
            dist2[ptr.first] = dist2[x] + ptr.second; 
            dfs3(ptr.first, x); 
        }
    }
}

void dfs4(int x, int p) {
    for (auto ptr: g[x]) {
        if (ptr.first != p) {
            dist3[ptr.first] = dist3[x] + ptr.second; 
            dfs4(ptr.first, x); 
        }
    }
}

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++) {
        dist1[i] = 0, dist2[i] = 0;
        vis[i] = false;
    } 
    vector<int> diams, anss;
    for (int i = 0; i < N; i++) {
        if (!vis[i]) {   
            dijametar.clear();
            vec.clear(); 
            dfs(i, -1);  
            int mx = 0, root = 0; 
            for (int x: vec) { 
                if (mx < dist1[x]) {
                    root = x;
                    mx = dist1[x];
                }
            }  
            dfs2(root, -1);
            int diamend = 0;
            mx = -1; 
            for (int x: vec) {
                if (mx < dist2[x]) {
                    mx = dist2[x];
                    diamend = x;
                }
            }      
            while (diamend != -1) {  
                dijametar.push_back(diamend); 
                diamend = par[diamend];
            }     
            int diff = (int)(2e9), cen = 0, krc = 0;
            for (int x: dijametar) {  
                if (diff > abs(mx - 2 * dist2[x])) {
                    diff = abs(mx - 2 * dist2[x]); 
                    cen = x; 
                    krc = dist2[x]; 
                }
            }
            vv.push_back(make_pair(max(krc, mx - krc), cen));
        }
    }    
    sort(rall(vv));
    for (int i = 1; i < vv.size(); i++) {
        g[vv[0].second].push_back({vv[i].second, L});
        g[vv[i].second].push_back({vv[0].second, L}); 
    }
    for (int i = 0; i < N; i++) {
        dist2[i] = 0, dist3[i] = 0;
    }
    dfs3(0, -1);
    int st = 0, distance = 0;
    for (int i = 0; i < N; i++) {
        if (distance < dist2[i]) {
            distance = dist2[i];
            st = i;
        }
    }
    dfs4(st, -1);
    int ans = 0;
    for (int i = 0; i < N; i++) {
        ans = max(ans, dist3[i]);
    }
    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 
*/

Compilation message (stderr)

dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:106:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  106 |     for (int i = 1; i < vv.size(); i++) {
      |                     ~~^~~~~~~~~~~

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