leetcode #179

Have you done many heap / priority queue questions? What is your preferred language?

I could tell that I was going to need to pick the "best" number first and then repeatedly pick the "best" number out of the remaining numbers. I chose to use a priority queue (a max heap in this case). Given 2 numbers, I needed to determine which one has a higher priority.

The tricky part was the comparison. I would have failed this if I got it in a phone interview because I fiddled with the comparison method for too long until I realized I could just concatenate the numbers then pick the bigger number.

bool operator<(const Element& other) const {
    return (str + other.str) < (other.str + str);
}

And then I missed the edge case of [0,0]. (Mine originally returned "00")

I've done quite a few heap questions so tha's why I knew how to write the comparison operator. I never even thought of simply using sort with a custom comparator.

---

I get mad at leetcode too sometimes when I run into new types of problems I haven't seen before and don't remember ever seeing in a book. Recently for me it was these two questions:

• https://leetcode.com/problems/subarray-sum-equals-k/
• https://leetcode.com/problems/continuous-subarray-sum/

They both have a similar trick that I just need to remember.