LIS and LowerBound

#pragma warning(disable:4996)
#include<cstdio>
int mylower_bound(int *arr,int n,int key)
{
    int start=0;
    int end=n;
    int mid;
    while(start<end)
    {
        mid=(start+end)/2;
        if(arr[mid]<key)
        {
            start=mid+1;
        }
        else
        {
            end=mid;
        }
    }
    return end;
}
int main(void)
{
    /*
    int n, arr[1000000],ans[1000000];
    scanf("%d",&n);
    for(int i=0;i<n;i++)
    {
        scanf("%d",&arr[i]);
    }
    */
    int arr[6]={10,20,10,30,20,50};
    int ans[6];
    ans[0]=arr[0];
    int anslength=1;
    for(int i=1;i<6;i++)
    {
        int tmp=mylower_bound(ans,anslength,arr[i]);
        if(tmp>=anslength)
        {
            ans[tmp]=arr[i];
            anslength++;
        }
        else
        {
            ans[tmp]=arr[i];
        }
    }
    printf("%d",anslength);
}