Problems
November 29, 2022
Inorder successor in BST
As we are traversing a binary search tree, we can use it's property to find the inorder successor. The inorder successor of a node is the leftmost node in the right subtree. If the node does not have...
ReadNovember 29, 2022
Longest subarray of 1s after deleting one element
We will use two pointers to keep track of the start and end of the subarray. We will use a variable to keep track of the number of zeros in the subarray. If the number of zeros is less than or equal...
ReadNovember 29, 2022
Valid palindrome III
We will solve the problem using top-down dynamic programming. If the first and last characters are the same, we will check if the substring between the first and last characters is a valid...
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Generate a string with characters that have odd counts
If n is odd, we will return a string with n 'a's. If n is even, we will return a string with n-1 'a's and one 'b'.
Time complexity: O(n), n is the number of characters in the string...
November 29, 2022
Count of smaller numbers after self
We will make a sorted copy of the nums. Then we iterate over each number, find the index of the number in the sorted copy, and add the number of numbers smaller than the number to the result. Time...
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Reverse words in a string II
We will reverse the entire string, then reverse each word. We will use two pointers to keep track of the start and end of each word.
Time complexity: O(n), n is the length of the...
November 28, 2022
Count number of bad pairs
Rather counting the number of bad pair, we can count the number of good pair and substruct it from to total number of pairs to get the number of bad pairs. For an array of size n, there are exactly n...
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Design phone directory
We will use a set to keep track of the available numbers. We will also use a queue to keep track of the numbers that have been released.
Time complexity: O(1)
Space complexity:...
November 28, 2022
Shortest word distance
We will keep track of both words' last seen index. Then we will iterate through the words array and update the result if we find either of the words. Finally, we will return the result....
November 28, 2022
Count nodes equal to sum of descendants
We will use DFS in post order traversal to solve the problem. We will recursively call the function on the left and right child of the root. Then we will check if the sum of the left and right child...
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