Submission #1065480

#	Time	Username	Problem	Language	Result	Execution time	Memory
1065480		vjudge1	Longest Trip (IOI23_longesttrip)	C++17	100 / 100	13 ms	600 KiB

longesttrip

#include "longesttrip.h"
#include<bits/stdc++.h>
using namespace std;
int findit(vector<int>v,vector<int>vf){
    if(v.size()==1)return v[0];
    vector<int>v1,v2;
    for(auto i:v)
        v1.push_back(i),
        swap(v1,v2);
    if(are_connected(v1,vf))
        return findit(v1,vf);
    return findit(v2,vf);
}
mt19937 rng(0);
vector<int> longest_trip(int N, int D){
    vector<int>path1,path2,v(N);
    iota(v.begin(),v.end(),0);
    shuffle(v.begin(),v.end(),rng);
    path1={v[0]},path2={v[1]};
    for(int i=1;i*2+1<N;i++){
        int U=v[i*2],V=v[i*2+1];
        int a=are_connected({U},{path1.back()});
        if(are_connected({U},{V})){
            int b=are_connected({U},{path2.back()});
            if(a) path1.push_back(U),
                path1.push_back(V);
            else if(b)
                path2.push_back(U),
                path2.push_back(V);
            else{ reverse(path2.begin(),path2.end());
                for(auto i:path2)
                    path1.push_back(i);
                path2 = {U,V};
            }
        } else {
            if(!a) swap(U,V);
            path1.push_back(U);
            if(are_connected({path2.back()},{V}))
                path2.push_back(V);
            else {reverse(path2.begin(),path2.end());
                for(auto i:path2)
                    path1.push_back(i);
                path2 = {V};
            }
        }
    }
    if(N%2){
        int X=v.back();
        int a=are_connected({X},{path1.back()});
        int b=are_connected({X},{path2.back()});
        if(a) path1.push_back(X);
        else if(b)path2.push_back(X);
        else{ reverse(path2.begin(),path2.end());
            for(auto i:path2)
                path1.push_back(i);
            path2 = {X};
        }
    }
    if(!are_connected(path1,path2))
        return path1.size()>path2.size()?path1:path2;
    vector<int>A(1,path1[0]),B(1,path2[0]);
    if(path1.size()>1)A.push_back(path1.back());
    if(path2.size()>1)B.push_back(path2.back());
    if(are_connected(A,B))
        for(int i=0;i<A.size();i++)
            for(int j=0;j<B.size();j++)
                if(are_connected({A[i]},{B[j]})) {
                    if(!i)reverse(path1.begin(),path1.end());
                    if(j) reverse(path2.begin(),path2.end());
                    for(auto i:path2) path1.push_back(i);
                    return path1;
                }
    int X=findit(path1,path2);
    int Y=findit(path2,{X});
    while(path1.back()-X)
        path1.push_back(path1[0]),
        path1.erase(path1.begin());
    while(path2[0]-Y)
        path2.push_back(path2[0]),
        path2.erase(path2.begin());
    for(auto i:path2)
        path1.push_back(i);
    return path1;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:65:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |         for(int i=0;i<A.size();i++)
      |                     ~^~~~~~~~~
longesttrip.cpp:66:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |             for(int j=0;j<B.size();j++)
      |                         ~^~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 60 / 60