spoj Stock Exchange

#include <cstdio>
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

typedef long long ll;

vector<ll> LIS(vector<ll> X){
    ll n = X.size(), L = 0, M[n+1], P[n];
    ll lo,hi,mi;
    
    L = 0;
    M[0] = 0;
    
    for(int i=0,j;i<n;i++){
        lo = 0; hi = L;
        
        while(lo!=hi){
            mi = (lo+hi+1)/2;
            
            if(X[M[mi]]<X[i]) lo = mi;
            else hi = mi-1;
        }
        
        j = lo;
        
        P[i] = M[j];
        
        if(j==L || X[i]<X[M[j+1]]){
            M[j+1] = i;
            L = max(L,(ll)j+1);
        }
    }
    
    ll a[L];
    
    for(int i=L-1,j=M[L];i>=0;i--){
        a[i] = X[j];
        j = P[j];
    }
    
    return vector<ll>(a,a+L);
}