UVA 481

http://uva.onlinejudge.org/external/4/481.html

#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 (size_t i = 1; i < a.size(); i++) 
        {
                // If next element a[i] is greater than last element of current longest subsequence a[b.back()], just push it at back of "b" and continue
  if (a[b.back()] < a[i]) 
                {
   p[i] = b.back();
   b.push_back(i);
   continue;
  }
 
                // Binary search to find the smallest element referenced by b which is just bigger than a[i]
                // Note : Binary search is performed on b (and not a). Size of b is always <=k and hence contributes O(log k) to complexity.    
  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;
  }
 
                // Update b if new value is smaller then previously referenced value 
  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;
}
 
/* Example of usage: */
#include <cstdio>
int main()
{
 int a[100000],i=0;
 
 while(scanf("%d",&a[i])!=EOF)
  i++;
 vector<int> seq(a, a+i); // seq : Input Vector
 vector<int> lis;                              // lis : Vector containing indexes of longest subsequence 
        find_lis(seq, lis);
 
        //Printing actual output 
        printf("%d\n-\n",lis.size());
 for (size_t i = 0; i < lis.size(); i++)
  printf("%d\n", seq[lis[i]]);   
 
 return 0;
}