Problems
August 20, 2022
Number of pairs of strings with concatenation equal to target
First we will count the number of frequency of each elements of the input. Then iterate over all possible slices of target and multiply by the count and add it to our final result. If some slices are...
ReadAugust 20, 2022
The k weakest rows in a matrix
First we iterate through the whole matrix to count the number of 1's in the matrix and put it in an min heap. Then we extract top k elements from that heap. Time Complexity:...
ReadAugust 19, 2022
Design parking system
We will create a hashmap, with the capacity. Each time, we add a car, we decrease the capacity by 1. If the capacity is already filled up, we return false, otherwise return true. Time Complexity:...
ReadAugust 19, 2022
Split array into consecutive subsequences
First we will count all the numbers. Then we will create a second hashmap to keep track of subsequences. Then we iterate over the input array, then if there is already a subsequence in place, we add...
ReadAugust 18, 2022
Reduce array size to the half
We will count the values, then sort them. Then we start removing item from the most common elements and count them. When the removed elements reach more than half of the input array, we return the...
ReadAugust 18, 2022
Strange printer
If we start from the last character, then it will always print with 1 switch. This will be our base case. We will run DFS to the rest of the characters. Then we will look through each elements until...
ReadAugust 17, 2022
Beautiful arrangement
Generate the array of numbers that will be used to create permutations of 1 to n (n inclusive) ex: 3 will become [1, 2, 3]. Then, iterate through all elements in the list and compare it to i which is...
ReadAugust 17, 2022
Unique morse code words
We will translate each word to a morse code and then add that to a set. Finally return the number of elements of that set.
Time Complexity: O(n*m), n is the number of words, m is...
August 16, 2022
Find triangular sum of an array
This problem is basically reverse pascal's triangle. For the ith element of one level, we can calculate it from the i and i+1 th element from the previous level and mod the result by 10. After each...
ReadAugust 16, 2022
First unique character in a string
First we will count each character of the string. Then we iterate from the beginning, check which character has character count 1, return that. If we can't find anything with character count 1, we...
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