Problems
November 1, 2022
Minimum absolute difference in bst
We will traverse the tree with inorder traversal, that way we will get a sorted array. We will keep track of the minimum difference between two consecutive elements in the array, return it as the...
ReadNovember 1, 2022
Minimum swaps to group all 1s together II
We will count number of ones in nums, let the number of ones be stored in the variable ones. Append nums to nums because we have to look at it as a circular array. Find the maximum...
November 1, 2022
Where will the ball fall
We drop the ball at grid[0][c] and track ball position c1, which initlized as c. An observation is that, if the ball wants to move from c1 to c2, we must have the board direction grid[r][c1] ==...
ReadOctober 31, 2022
Find all possible recipes from given supplies
We will create a graph where each node represents a recipe and each edge represents a supply. We will iterate over the recipes and add the edges to the graph. We will use topological sort to solve...
ReadOctober 31, 2022
Optimal division
Regardless of parentheses, every element is either in the numerator or denominator of the final fraction. The expression nums[0] / ( nums[1] / nums[2] / ... / nums[n-1] ) has every element in the...
ReadOctober 31, 2022
Pairs of songs with total durations divisible by 60
Calculate the time % 60 then it will be exactly same as two sum problem.
Time complexity: O(n)
Space complexity: O(n)
October 31, 2022
Toeplitz matrix
We will iterate over the rows and columns and compare diagonally adjacent elements. If they are not equal, we can return false. If we reach the end of the loop, we can return true. Time...
ReadOctober 30, 2022
Shortest path in a grid with obstacles elimination
We will use a queue to store the nodes that we need to visit. We will also use a set to store the nodes that we have already visited. We will traverse the grid in a breadth-first manner. If the...
ReadOctober 30, 2022
Divide array into equal pairs
We can use a hashmap to store the frequency of each element in the array. Then we can iterate over the array and check if the frequency of the current element is even or not. If it is even, we can...
ReadOctober 30, 2022
Valid number
We cal also use 3 flags for met_dot, met_e and met_digit. We can iterate over the string and update the flags. If the current character is a digit, we can set met_digit to true. If the current...
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