Anshul

[aanshul20]

Merged all the new changes with undo

[nus-se-pr-bot]

Hi @aanshul20, your pull request title is invalid. It should be in the format of [Activity ID][Team ID] Your name, where [Activity Id] has no dashes or spaces (e.g. [T2A3] stands for Tutorial 2 Activity 3) and [Team ID] has one dash only and no spaces (e.g. [W14-A2] means Wednesday 2pm (14 hrs), Phase A, Team 2). Please follow the instructions given strictly and edit your title for reprocessing.

Submit only one activity per pull request (unless otherwise stated in instructions) and do remember to create your branches from the commit where the master branch is pointing at so that each PR you submit only consist of commits meant for the activity.

Note: this comment is posted by a bot. If you believe this is done in error, please create an issue at cs2103-pr-bot and add a link to this PR.