Submission #1073715

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073715		andrewp	Dreaming (IOI13_dreaming)	C++14	14 / 100	38 ms	13784 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 dp[mxN], dpp[mxN], ps[mxN], ss[mxN];
int current_root = 0, sz = 0;
bool vis[mxN];  
vector<int> vec;

void dfs1(int x, int p) {
    sz++;
    vis[x] = true;   
    vec.push_back(x);  
    for (auto ptr: g[x]) {
        if (ptr.first != p) {  
            dfs1(ptr.first, x);
            dp[x] = max(dp[x], dp[ptr.first] + ptr.second);     
        }
    }
} 

void dfs2(int x, int p) {  
    for (auto ptr: g[x]) {
        if (ptr.first != p) {    
            if (x == current_root) {
                dpp[ptr.first] += ptr.second; 
            } else {
                dpp[ptr.first] = dpp[x] + ptr.second;
            }
            dfs2(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++) {
        dp[i] = 0, dpp[i] = 0;
    }
    vector<int> diams, anss;
    for (int i = 0; i < N; i++) {
        if (!vis[i]) { 
            vec.clear();  
            sz = 0; 
            dfs1(i, -1);  
            if (sz == 1) {
                continue; 
            }
            ps[0] = dp[g[i][0].first] + g[i][0].second;  
            for (int j = 1; j < g[i].size(); j++) {    
                ps[j] = max(ps[j - 1], dp[g[i][j].first] + g[i][j].second);   
            }         
            for (int j = g[i].size() - 1; j >= 0; j--) { 
                ss[j] = max(ss[j + 1], dp[g[i][j].first] + g[i][j].second); 
            }  
            for (int j = 0; j < g[i].size(); j++) { 
                dpp[g[i][j].first] = max((j >= 1 ? ps[j - 1] : 0), ss[j + 1]);   
            }  
            for (int j = 0; j <= g[i].size() + 5; j++) {
                ps[j] = 0, ss[j] = 0;
            }    
            current_root = i; 
            dfs2(i, -1); 
            int mn = (int)(2.1e9), di = 0;
            for (int x: vec) {  
                // cerr << i << ' ' << x << ' ' << dp[x] << ' ' << dpp[x] << '\n';  
                mn = min(mn, max(dpp[x], dp[x]));
                di = max(di, dpp[x] + dp[x]); 
            }
            diams.push_back(di); 
            anss.push_back(mn);  
        } 
    }    
    int ans = max(diams[0], diams[1]); 
    ans = max(ans, anss[0] + anss[1] + 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 
*/

Compilation message (stderr)

dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:63:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   63 |             for (int j = 1; j < g[i].size(); j++) {
      |                             ~~^~~~~~~~~~~~~
dreaming.cpp:69:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   69 |             for (int j = 0; j < g[i].size(); j++) {
      |                             ~~^~~~~~~~~~~~~
dreaming.cpp:72:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   72 |             for (int j = 0; j <= g[i].size() + 5; j++) {
      |                             ~~^~~~~~~~~~~~~~~~~~

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