HackerRank "Poisonous Plants"

I had the same BFS idea as one of the AC code this: because dying pattern is spead from the initial dying ones :)

#include <iostream>
#include <queue>
#include <vector>
using namespace std;

int main()
{
    int N; cin >> N;
    vector<int> P(N + , -);

    //    Dancing Links
    vector<int> pre(N + );
    vector<int> nex(N + );

    //    Markers
    vector<int> day(N + );

    for(int i  = ; i < N; i ++)
    {
        cin >> P[i];
    }    

    //    Fill initial queue
    queue<int> q;
    for(int i = N-; i > ; i--)
    {
        pre[i]=i-;
        nex[i]=i+;
        if(P[i] > P[i-])
        {
            day[i]=;
            q.push(i);
        }
    }

    int ans = ;
    while(!q.empty())
    {
        int cur=q.front();    q.pop();
        ans = day[cur];

        //    Dis-link current index
        pre[nex[cur]]=pre[cur];
        nex[pre[cur]]=nex[cur];

        if(P[nex[cur]] > P[pre[cur]]){
            day[nex[cur]] = day[cur]+;
            q.push(nex[cur]);
        }
    }
    cout << ans << endl;
    return ;
}