Cod sursa(job #874358)

Utilizator Tzappy90Mihalache Constantin Tzappy90 Data 8 februarie 2013 11:13:21
Problema Subsir crescator maximal Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.73 kb
#include <vector>
#include <fstream>
using namespace std;
ifstream f("scmax.in");
ofstream g("scmax.out");
int a[100000];
/* 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 n;
int main()
{
    f>>n;
	for(int i=0; i<n; i++)
        f>>a[i];
	vector<int> seq(a, a+sizeof(a)/sizeof(a[0])); // seq : Input Vector
	vector<int> lis;                              // lis : Vector containing indexes of longest subsequence
        find_lis(seq, lis);

        //Printing actual output
    g<<lis.size()<<'\n';
	for (size_t i = 0; i < lis.size(); i++)
		g<<seq[lis[i]]<<' ';
    g<<'\n';

	return 0;
}