Submission #535423

#	Time	Username	Problem	Language	Result	Execution time	Memory
535423		AngusWong	Dreaming (IOI13_dreaming)	C++17	18 / 100	43 ms	16280 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
#define pii pair<int, int>
#define f first
#define s second
using namespace std;

int n, m, l, dis[100001], leaf[100001], len, stp, edp, ans;
vector<pii> v[100001];
vector<int> path, mx;

void dfs(int x, int prev=-1){
    dis[x]=0;
    leaf[x]=x;
    int mx=x, mx2=x;
    for (pii i: v[x]){
        if (i.f==prev) continue;
        dfs(i.f, x);
        dis[i.f]+=i.s;
        if (dis[i.f]>dis[mx]) mx2=mx, mx=i.f;
        else if (dis[i.f]>dis[mx2]) mx2=i.f;
    }
    if (dis[mx]+dis[mx2]>len) len=dis[mx]+dis[mx2], stp=leaf[mx], edp=leaf[mx2];
    dis[x]=dis[mx];
    leaf[x]=leaf[mx];
}

bool get_path(int x, int prev=-1){
    if (x==edp) return true;
    for (pii i: v[x]){
        if (i.f==prev) continue;
        if (get_path(i.f, x)){
            path.push_back(i.s);
            return true;
        }
    }
    return false;
}

int max_length(int x){
    len=stp=edp=-1;
    dfs(x);
    path.clear();
    get_path(stp);
    if (path.empty()) return 0;
    for (int i=1; i<path.size(); i++) path[i]+=path[i-1];
    int ans=2e9;
    for (int i=0; i<path.size(); i++){
        int t=path[i]; // 0..i
        if (i<path.size()) t=max(t, path[path.size()-1]-path[i]);
        ans=min(ans, t);
    }
    return ans;
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    n=N, m=M, l=L;
    for (int i=0; i<m; i++){
        v[A[i]].push_back({B[i], T[i]});
        v[B[i]].push_back({A[i], T[i]});
    }
    for (int i=0; i<n; i++) dis[i]=-1;
    for (int i=0; i<n; i++){
        if (dis[i]==-1) mx.push_back(max_length(i));
    }
    sort(mx.begin(), mx.end(), greater<int>());
    ans=mx[0];
    if (mx.size()>1) ans=max(ans, mx[0]+mx[1]+l);
    if (mx.size()>2) ans=max(ans, mx[1]+mx[2]+l*2);
    return ans;
}

Compilation message (stderr)

dreaming.cpp: In function 'int max_length(int)':
dreaming.cpp:46:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |     for (int i=1; i<path.size(); i++) path[i]+=path[i-1];
      |                   ~^~~~~~~~~~~~
dreaming.cpp:48:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |     for (int i=0; i<path.size(); i++){
      |                   ~^~~~~~~~~~~~
dreaming.cpp:50:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |         if (i<path.size()) t=max(t, path[path.size()-1]-path[i]);
      |             ~^~~~~~~~~~~~

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