Submission #724430

#	Time	Username	Problem	Language	Result	Execution time	Memory
724430		Dan4Life	Dreaming (IOI13_dreaming)	C++17	47 / 100	1075 ms	17836 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
const int mxN = (int)1e5+10;
const int INF = (int)2e9;
int n, m, l;
vector<int> path;
vector<pair<int,int>> v, adj[mxN];
int vis[mxN];
int dis[mxN];
int CC=1;

bool dfs2(int s, int p, int t){
    if(s==t) return 1;
    for(auto x : adj[s]){
        int u = x.fi, w = x.se;
        if(u==p) continue;
        if(dfs2(u,s,t)){ path.pb(w); return 1; }
    }
    return 0;
}

void dfs(int s, int p){
    vis[s]=CC;
    for(auto x : adj[s]){
        int u = x.fi, w = x.se;
        if(u==p) continue;
        dis[u] = dis[s]+w;
        dfs(u,s);
    }
}

void calcDiam(int s){
    int a, b, mx = 0;
    dis[s]=0; dfs(s,-1);
    for(int i = 1; i <= n; i++)
        if(vis[i]==CC and mx<=dis[i]) mx=dis[i],a=i;
    dis[a]=0; mx = 0; dfs(a,-1);
    for(int i = 1; i <= n; i++)
        if(vis[i]==CC and mx<=dis[i]) mx=dis[i],b=i;
    path.clear(); dfs2(a,-1,b);
    int dis1 = accumulate(all(path),0), dis2 = 0;
    int ans = dis1, diam=dis1;
    for(auto u : path){
        dis1-=u, dis2+=u;
        ans = min(ans, max(dis1,dis2));
    }
    v.pb({ans,diam});
}

int travelTime(int N, int M, int L, int a[], int b[], int c[]) {
    n = N; m = M; l = L;
    for(int i = 0; i < m; i++){
        a[i]++, b[i]++;
        adj[a[i]].pb({b[i],c[i]});
        adj[b[i]].pb({a[i],c[i]});
    }
    for(int i = 1; i <= n; i++)
        if(!vis[i]) calcDiam(i),CC++;
    int ans = INF, ans2=0;
    sort(all(v));
    for(int i = 0; i < sz(v); i++)
        ans2 = max(ans2, v[i].se);
    for(int i = 0; i < sz(v); i++){
        int d1 = v[i].fi, d2 = -1;
        vector<int> xd; xd.clear();
        for(int j = sz(v)-1; j>=0; j--){
            if(i==j) continue;
            xd.pb(v[j].fi);
            if(sz(xd)==2) break;
        }
        int sum = 0;
        if(sz(xd)>=1) sum = max(sum, d1+l+xd[0]);
        if(sz(xd)>=2) sum = max(sum, xd[0]+l*2+xd[1]);
        if(sz(xd)>=1) ans = min(ans, sum);
    }
    return max(ans, ans2);
}

Compilation message (stderr)

dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:70:27: warning: unused variable 'd2' [-Wunused-variable]
   70 |         int d1 = v[i].fi, d2 = -1;
      |                           ^~
dreaming.cpp: In function 'void calcDiam(int)':
dreaming.cpp:46:23: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
   46 |     path.clear(); dfs2(a,-1,b);
      |                   ~~~~^~~~~~~~
dreaming.cpp:46:23: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]

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