Longest Increasing Subsequence 2

#include <iostream>
#include <vector>
using namespace std;
/* Finds longest strictly increasing subsequence. O(n log k) algorithm. */
void find_lis(vector<int> &a, vector<int> &b)
{
    vector<int> p(a.size());
    int u,v;
    if(a.empty()) return;
    b.push_back(0);
    for(int i=1; i<a.size(); i++)
    {
        // Add element to LIS
        if(a[b.back()]<a[i])
        {
            p[i] = b.back();
            b.push_back(i);
            continue;
        }
        // Binary Search in current LIS an index u which is an element just larger than a[i]
        for(u=0,v=b.size()-1; u<v;)
        {
            int c = (u+v)/2;
            if(a[b[c]]<a[i]) u = c+1;
            else v = c;
        }
        // If u is found, then update
        if(a[i]<a[b[u]])
        {
            if (u > 0) p[i] = b[u-1];
            b[u] = i;
        }
    }
    for (u = b.size(), v = b.back(); u--; v = p[v]) b[u] = v;
}
int main()
{
    int a[] = {10,22,11,2,4,91,17,18,21,41,8};
    vector<int> seq(a, a+sizeof(a)/sizeof(a[0]));
    vector<int> lis;
    find_lis(seq, lis);
    for (int i = 0; i < lis.size(); i++)
        cout<<seq[lis[i]]<<" ";
    return 0;
}