Submission #1037565

#	Time	Username	Problem	Language	Result	Execution time	Memory
1037565		sleepntsheep	Thousands Islands (IOI22_islands)	C++17	Compilation error	0 ms	0 KiB

islands

#include "islands.h"

#include <variant>
#include <vector>
#include<set>
using namespace std;

std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {
    vector<vector<int>> a(N);
    for (int i = 0; i < M; ++i)
        a[U[i]].push_back(i);

    int is_sub2 = N<=400;
    static int id[401][401];
    if(N<=400){
        memset(id, -1, sizeof id);
        for(int i=0;i<M;++i)id[U[i]][V[i]]=i;
        for(int i=0;i<N;++i)for(int j=i+1;j<N;++j)
            if(id[i][j]==-1 ||id[j][i]==-1)is_sub2=0;
    }

    if (N==2){
        if(a[0].size()>=2&&a[1].size()){
            int a1=a[0][0],a2=a[0][1],a3=a[1][0];
            return vector<int>{a1, a3, a2, a1, a3, a2};
        }
        return false;
    }else if(is_sub2){
        int a1=id[0][1],a2=id[1][0],a3=id[1][2],a4=id[2][1],a5=id[2][0],a6=id[0][2];
        return vector<int>{a1,a3,a5,a6,a4,a2,a5,a3,a1,a2,a4,a6};
    }else{
        set<pair<int,int>>w;
        for(int i=0;i<M;++i)w.emplace(U[i],V[i]);
        for(int i=1;i<N;++i)for(int j=i+1;j<N;++j){
            if(w.count({0,i})+w.count({i,j})+w.count({j,0})==3){
                int a1=id[0][i],a2=id[i][0],a3=id[i][j],a4=id[j][i],a5=id[j][0],a6=id[0][j];
                return vector<int>{a1,a3,a5,a6,a4,a2,a5,a3,a1,a2,a4,a6};
            }
            return false;
        }
    }
}

Compilation message (stderr)

islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:17:9: error: 'memset' was not declared in this scope
   17 |         memset(id, -1, sizeof id);
      |         ^~~~~~
islands.cpp:6:1: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    5 | #include<set>
  +++ |+#include <cstring>
    6 | using namespace std;
islands.cpp:10:28: warning: control reaches end of non-void function [-Wreturn-type]
   10 |     vector<vector<int>> a(N);
      |                            ^