Binsearch

bool binsearch(std::vector<int> &table, int key)
{
    int l = 0, r = table.size() - 1;

    while(l <= r)
    {
        int m = l + (r - l) / 2;

        if(table[m] == key) return true;
        if(table[m] > key)  r = m - 1;
        else                l = m + 1;
    }

    return false;
}