<aside> ⚠️ Here are some interesting and useful tips for navigating through LeetCode. The majority of the code snippets are written in Python.
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ListNode object (linked list) ← used often in the questions.
Prefix sum (in linked list)
Prefix sum (array): of [1, 2, 3, 4, 5] is [1, 3, 6, 10, 15].
nums = [1, 2, 3, 4, 5]
prefix_sum = [nums[0]]
for i in range(1, len(nums)):
prefix_sum.append(prefix_sum[-1] + nums[i])
Remove nodes in linked list
Replace an array completely with another
arr[:] = new_arr
Use dict.fromkeys(arr) to keep the order of elements, set(arr) doesn’t keep the order!
list(dict.fromkeys([-1,0,0,0,0,3,3])) # [-1, 0, 3]
list(set([-1,0,0,0,0,3,3])) # [0, 3, -1]
“non-decreasing order” = the elements in the array are not strictly ascending like [1,2,3,4,5], it could be [1,1,2,2,3].
In LeetCode, the Runtime result isn’t consistent.
Brute Force: An algorithm that generates and tests all possibilities until it finds a solution. While not efficient, it assures an answer if one exists.