Longest subsequence (DP algorithm)

#include <bits/stdc++.h>

#define MAX 100000+10

#define INF 100000000

using namespace std;

int a[MAX],c[MAX],len;

int main()

{

    int n,j;

    while(scanf("%d",&n)!=EOF)

    {

        for(int i=0; i<n; i++)

            scanf("%d",&a[i]);

        len=0;

        c[0]=-INF;

        for(int i=0; i<n; i++)

        {

 

            if(a[i]>c[len]) j=++len;

            else j= lower_bound(c,c+len,a[i]) - c;

            c[j]=a[i];

        }

        printf("%d\n",len);

    }

}