In Memoriam – Prof. Ajit A. Diwan

“Prof. Diwan enters the class — short-statured, lanky, dressed in extremely plain and simple clothes — and starts rubbing the board. We thought of him as an ordinary professor. It was CS201, Data Structures and Algorithms, and we hadn’t yet understood the magnitude of this course. And then he started teaching us in his stentorian voice and amazing grasp of concepts.”

This is just one of the many retellings that students, ex-students, and professors from all over the world have poured in for Prof. Ajit Diwan, who passed away on the 19th of January 2025.

Prof. Ajit Diwan, a stalwart from the CSE department at IIT Bombay has been widely recognized as one of the leading figures in graph theory in India. Having graduated from IIT Bombay with a BTech. in Electrical Engineering in 1983, he went on to pursue his PhD at Tata Insitute of Fundamental Research (TIFR), Bombay and completed it in 1989. Life brought him around on a full circle as he joined IIT Bombay as a faculty member in 1988, beginning a journey of a little less than three decades that left a lasting impression on thousands of his students and colleagues.

His passing away drew a lot of heartfelt and indelible memories from his ex-students across the years. “Taking his Data Structures and Algorithms course was like a rite of passage for our sophomore BTech class. Might have felt like the hardest class I had taken and easily one of the few courses which have stuck in my mind all these years,” mentioned B. Aditya Prakash, an IITB graduate from the batch of 2007. He described Prof. Diwan as ‘disarmingly straightforward, sharp, and inspiring’. 

Prof. Diwan’s primary research interests revolved around graph theory, combinatorics, and algorithms. He made notable contributions to the study of 2-factors, triangle factors, and clique factors in planar, cubic, and edge-colored graphs, along with partitioning and decomposing graphs under various constraints. He taught a variety of courses during his time here, among the recent ones being CS218 Design and Analysis of Algorithms, and CS608 Approximation Algorithms. He was also teaching CS755 Competitive Programming this semester.

All of the heartfelt messages for Prof. Diwan shared a common recognition of him as an exceptional academic with sheer brilliance in breaking down conventionally difficult topics into easy-to-understand discussions. Armed with his humility and simplicity, Prof. Diwan’s influence on his students has stood the test of time. In an emotional and wholesome in-memoriam for Prof. Diwan on the CSE department website by Ashwin (batch of 2014), one of his ex-students, he recalls his teaching – “No matter where you’re from or how you look, if you know your stuff, people will listen to you.”

With a knack for engaging in profound discussions, Prof. Diwan has widely been understood to have tackled the most difficult of problems in the field of algorithms head-on. Although students agreed in good spirit that his tests were notoriously hard to score well in, they did not shy away from characterizing him as ‘comprehensively competent’. Emulating this emotion, Sankeerth Rao Karingula, an IITB alumnus from the batch of 2014, recalled, “…once I asked him about a variant of the Huffman algorithm and by the next class he had a completely different algorithm for that variant, and he was so excited to explain it to me after the class with his eyes beaming.” In this spirit, Raj Dabre, an incoming visiting Assistant Professor at IIT Bombay, who had spent some time with Prof. Diwan, also remarked, “As a professional, he was a no-nonsense person and was laser-focused on his work. However, he always was willing to help students with their doubts. …Truly a man dedicated to his craft above all else.” 

Insight also reached out to some CSE students in the institute who had the opportunity to interact with him. “…a very talented teacher who teaches in a clean and precise way”, mentioned Sreyas. Another student, Lokesh, remarked, “He was a very enthusiastic teacher interested in seeing everyone’s thought process by correcting everyone’s papers all by himself.”

In a candid remembrance, Rajat Jain, an IITB alumnus from the batch of 2006, shared with Insight his memorable experience with Prof. Diwan –

“The first class that I attended of Prof. Diwan is still fresh in my mind. ….This course with Prof. Diwan became a journey in itself. Every single problem that Sir shared was a project in itself that only a handful of students could crack. We dreaded sitting in his quizzes and semester examinations and scored poorly. Solving even one of his problems used to feel like a victory! And yet, the magnitude of learning we achieved in Sir’s class was second to none. We couldn’t crack his problems, but we were prepared to solve most other problems that came our way — especially useful when we used to sit for job interviews.”

All of these represent just a fraction of the diverse stories that people from different corners of the world have come forward to tell about Prof. Diwan. Remembered as a distinguished academic and humble mentor, professors like him are the face of IIT Bombay’s global reputation and enriching environment. Insight, on behalf of the IIT Bombay community, pays homage to his incredible journey at this institute and his unwavering commitment to the upliftment of his students. We also extend our deepest strength and support to Prof. Ajit Diwan’s family, friends, and colleagues during this time of great grief and loss.

In an email on January 23rd, Prof. Varsha Apte, Head of the CSE department, announced a memorial meeting at F.C. Kohli Auditorium on 29th January at 4:30 PM in honor of Prof. Diwan ‘to recall the myriad ways in which he made a positive difference in our lives’.

*The quotes from the ex-students have been sourced from the in-memoriam page on the CSE department website, and also the comments on Prof. Arindam Khan’s posts on LinkedIn and X with permission from the respective authors.

Editorial Credits: Rishit Kesharwani