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Monthly Archives: June 2019
Leetcode 44: Wildcard Matching
The obvious solution is to use a recursive function. If we find a wildcard then we recurse every position in s from that point onwards. The problem with this is that it is very slow if there are a lot … Continue reading
Leetcode 43: Multiply Strings
The general steps to do long multiplication are fairly straightforward but the implementation was a bit fiddly. I think it would be easier to to reverse the strings and work on them in reverse, then the least significant index will … Continue reading
Leetcode 42: Trapping Rain Water
This is a tricky leetcode problem. There are a few observations that need to be made. Water traps between two bars and only fills each of those gaps to a volume that is the gap’s height taken away from the … Continue reading
Leetcode 41: First Missing Positive
There are a few different ways to solve this including some ways that destroy some of the (out of bounds) values. My favoured solution keeps all the values but just rearranges them. I iterate through all the numbers and at … Continue reading
Leetcode 39: Combination Sum
This is a problem that fits naturally to a recursive solution. I’m not sure how I’d implement without recursion. The recursion automatically does a backtrack to find valid solutions. By starting the search for subitems from the current item and … Continue reading
Leetcode 37: Sudoku Solver
This was an interesting problem that highlights that sometimes it is better to write an algorithm for a computer to execute in a different way to how we would solve the problem with a human mind. So I first attempted … Continue reading