Submission #1074169

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074169		Trumling	Dreaming (IOI13_dreaming)	C++14	14 / 100	46 ms	15828 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];  
bool vis[mxN];
vector<int> vec, dijametar;
 
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);  
        }
    }
}  
 
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] && g[i].size()==1) { 
            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(i, -1);
            int diamend = 0;
            mx = 0; 
            for (int x: vec) {
                if (mx < dist2[x]) {
                    mx = dist2[x];
                    diamend = x;
                }
            }    
            diams.push_back(mx);
            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(dist2[x] - (mx - dist2[x]) )) {
                    diff = abs(dist2[x] - (mx - dist2[x]) );
                    cen = x;
                    krc = dist2[x];
                }
            }
            anss.push_back(max(krc, mx - krc));
        } 
    }     
    int ans = max(diams[0], diams[1]);
    ans = max(ans, anss[0] + anss[1] + L); 
    return ans;
}

Compilation message (stderr)

dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:54:25: warning: variable 'root' set but not used [-Wunused-but-set-variable]
   54 |             int mx = 0, root = 0;
      |                         ^~~~
dreaming.cpp:75:36: warning: variable 'cen' set but not used [-Wunused-but-set-variable]
   75 |             int diff = (int)(2e9), cen = 0, krc = 0;
      |                                    ^~~

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