Problems


September 5, 2022

House robber III

We will traverse the tree in DFS and take both with and without root result. Then we calculate the max from both of them and return the result. Time Complexity: O(n) Space...

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September 5, 2022

Basic calculator

We will take a stack. Initially our operation and operand will be 0 and + append each character to the stack. If the character is numeric, until we reach an operand we will calculate the...

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September 5, 2022

Longest absolute file path

Use stack to represent structure of a directory where the root of a directory is at index 0. Directory level can be infer from the number of tabs. ie "" is level 0, "\n" is level 1 and so on. Start...

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September 5, 2022

Course schedule IV

We will first create an adjacency list from the prerequisites. Then for each queires, we will start DFS from course 1 to course 2, if we can reach to course 2, then we append true in our result, else...

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September 5, 2022

All ancestors of a node in a directed acyclic graph

First we will create an ancestors adgacency list, where we can get the immediate parent of each node from the edge list. Then we will run DFS from each node, and get the node list of all reachable...

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September 5, 2022

Remove duplicate letters

We will create a hashmap to keep track of last occurance of the letters. Then we will have a visited hashset and a stack to keep track of the letters. We traverse sequentially on the string, for each...

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September 5, 2022

Search in rotated sorted array II

To solve this problem we have to follow the folllowing steps: Calculate the mid index. Check if the mid element == target, return True else move to next step. Else if the mid element >= left. If...

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September 5, 2022

Single number III

We will be using the XOR trick i.e n^n=0. During first traversal we will get the XOR of the required two numbers, then we will get the least significant bit of the XOR operation. This...

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September 5, 2022

Single number II

We will have 2 elements, one will be store all the values that store all the elements that occurs once and two will store all the elements that occurs twice. Then we make sure that the values that is...

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September 5, 2022

Basic calculator III

We will take a stack. Initially our operation and operand will be 0 and + append each character to the stack. If the character is numeric, until we reach an operand we will calculate the...

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