Pegasystems Software Engineer Interview Questions, Process, and Tips

Find common ancestor of 2 nodes in a binary tree

• Traverse the tree from root to both nodes and store the paths

• Compare the paths to find the last common node

• Use recursion to traverse the tree and find the common ancestor

To find the minimum element of a stack in O(1) time, maintain a separate stack for minimum values.

• Create a separate stack to store minimum values

• Push the minimum value onto the minimum stack every time a new value is pushed onto the main stack

• Pop the minimum stack every time the main stack pops a value

• The top of the minimum stack will always contain the minimum value

Sort a binary array of 0s and 1s and optimize the code.

• Use two pointers approach to swap 0s and 1s

• Avoid using sorting algorithms like bubble sort or selection sort

• Use a single loop to traverse the array and swap elements

• Use XOR operation to swap elements

Explaining Java HashMap internals and behavior when hashcode always returns 1.

• HashMap uses hashcode to calculate the index of the bucket where the key-value pair will be stored.

• If hashcode always returns 1, all key-value pairs will be stored in the same bucket resulting in poor performance.

• In this case, HashMap will use a linked list to store multiple key-value pairs in the same bucket.

• Retrieving a value from a HashMap...read more