Problems
August 11, 2022
Partition equal subset sum
This is basically a 0-1 knapsack problem, for each element, either we can take the element or leave it. First, we will check, if the sum of the numbers is not even, we immediately return false. Then...
ReadAugust 10, 2022
Word break
We can solve the problem using BFS. We can model the problem as graph, every index can be considered as vertex and every edge is a completed word. Then the problem just boiled down if the path...
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Convert sorted array to binary search tree
If there is no element in the sorted list, then we return null. This logic we will use as our base case. Then we will select the middle of the sorted list as our root node. Then from there, all the...
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Maximum product subarray
We will keep track of minimum and maximum products of each item and keep the current maximum is our result. When the whole traversal is done, we will return the maximum result. Time Complexity:...
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Partition labels
We will first count the last position of all chacracter in a hashmap. Then we will iterate through the string, check if the last index of the chacracter is equal to the current index, if yes, then we...
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Decode ways
We could decode a string with 1 character with just 1 way, but if we have a 2 digit string, then we can decode it 2 ways. For example, 12 can be decoded 1->A, b->2 or...
August 9, 2022
Binary trees with factors
We will convert the array to array set, so that we can do the lookup in constant time. Then we will check, if a candidate can divide the root without any remainder and root//candidate is available in...
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Valid parenthesis string
We will keep track of number of left parenthesis and number of right parenthesis in the string. For *, we could count it as left parenthesis or right parenthesis or we could ignore it....
August 9, 2022
Hand of straights
We will first check if the number of card is divisible by the group size, if not, we immediately return false. Then we count the number of cards, and create a min heap with all the distinct cards....
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Longest palindromic substring
We will create a helper function to count the number of palindrome in a string starting from a left and right pointers. For odd number, both will be same index, for even left and right pointers will...
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