• lower_bound

int find(vector<int> &a,int val)//lower_bound
{
    int l=0,r=a.size()-1;
    while(l<=r)
    {
        int mid=(l+r)>>1;
        if(a[mid]<val)l=mid+1;
        else 
            r=mid-1;
    }
    return l;
}

• upper_bound

int find(vector<int> &a,int val)//upper_bound
{
    int l=0,r=a.size()-1;
    while(l<=r)
    {
        int mid=(l+r)>>1;
        if(a[mid]<=val)l=mid+1;
        else 
            r=mid-1;
    }
    return l;
}