Submission #551369

#	Time	Username	Problem	Language	Result	Execution time	Memory
551369		razvan	Dreaming (IOI13_dreaming)	C++14	32 / 100	50 ms	12364 KiB

dreaming

#include "dreaming.h"
#include <iostream>
#include <cstdio>
#include <fstream>
#include <vector>
#include <algorithm>
#define pb push_back

using namespace std;
const int maxn = 100005;

struct xy {
    int x, y;
};
vector<xy> v[maxn];
int done[maxn];
int bgst[maxn], ibgst[maxn];
//int ibgst2[maxn];
int now = -1, inow;
//int lft, rgh;
int ansnow, iansnow;
void dfs(int x, int p) {
    done[x] = true;
    
    int big1 = 0, big2 = 0, ibig1 = -1, ibig2 = -1;
    for(auto u : v[x]) {
        if(u.x != p) {
            dfs(u.x, x);
            if(bgst[u.x] + u.y > big1) {
                big2 = big1;
                ibig2 = ibig1;

                big1 = bgst[u.x] + u.y;
                ibig1 = u.x;
            } else if(bgst[u.x] + u.y > big2) {
                big2 = bgst[u.x] + u.y;
                ibig2 = u.x;
            }
        }
    }
    bgst[x] = big1;
    ibgst[x] = ibig1;
    //ibgst2[x] = ibig2;
    if(big1 + big2 > now) {
        now = big1 + big2;
        inow = x;
    }
}
void dfs2(int x) {
    if(max(bgst[x], now - bgst[x]) < ansnow) {
        ansnow = max(bgst[x], now - bgst[x]);
        iansnow = x;
    }

    if(ibgst[x] != -1)
        dfs2(ibgst[x]);
}
vector<int> points;
int best = -1, ibest;
int travelTime(int n, int m, int l, int a[], int b[], int t[]) {
    int i, j;
    for(i = 0; i < m; i ++) {
        v[a[i]].pb({b[i], t[i]});
        v[b[i]].pb({a[i], t[i]});
    }
    for(i = 0; i < n; i ++) {
        if(done[i] == false) {
            done[i] = true;
            now = -1;
            dfs(i, -1);
            //lft = bgst[inow];
            //rgh = now - lft;
            ansnow = bgst[inow];
            iansnow = i;

            //cout << "now: " << now << ' ' << inow << "  " << ansnow << ' ' << iansnow << '\n';
            dfs2(ibgst[inow]);
            //cout << "ansnow: " << ansnow << ' ' << iansnow << '\n';

            points.pb(iansnow);
            if(ansnow > best) {
                best = ansnow;
                ibest = iansnow;
            }
        }
    }
    
    //cout << "best, ibest: " << best << ' ' << ibest << '\n';
    for(auto w : points) {
        //cout << "point " << w << '\n';
        if(w != ibest) {
            v[ibest].pb({w, l});
            v[w].pb({ibest, l});
        }
    }
    for(i = 0; i < n; i ++) {
        bgst[i] = ibgst[i] = 0;
        //ibgst2[i] = 0;
    }
    now = -1;
    dfs(0, -1);
    
    return now;
}

Compilation message (stderr)

dreaming.cpp: In function 'void dfs(int, int)':
dreaming.cpp:25:41: warning: variable 'ibig2' set but not used [-Wunused-but-set-variable]
   25 |     int big1 = 0, big2 = 0, ibig1 = -1, ibig2 = -1;
      |                                         ^~~~~
dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:61:12: warning: unused variable 'j' [-Wunused-variable]
   61 |     int i, j;
      |            ^

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