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Robert Endre Tarjan
Born April 30, 1948 (1948-04-30) (age 61)
Pomona, California
Fields Computer Science
Institutions Princeton University
Alma mater Caltech,
Known for Tarjan's off-line least common ancestors algorithm
Notable awards Turing Award

Robert Endre Tarjan (born April 30, 1948) is a renowned American computer scientist. He is the discoverer of several important graph algorithms, including Tarjan's off-line least common ancestors algorithm, and co-inventor of both splay trees and Fibonacci heaps.

He was born in Pomona, California.



Robert Tarjan's father was a child psychiatrist specializing in mental retardation, and ran a state hospital.[1] As a child, Tarjan read a lot of science fiction, and wanted to be an astronomer. He became interested in mathematics after reading Martin Gardner's mathematical games column in Scientific American. He became seriously interested in math in the eighth grade, thanks to a "very stimulating" teacher.

While he was in high school, Tarjan got a job, where he worked IBM card punch collators. He first worked with real computers at a summer science program in 1964.[1]

Tarjan obtained a Bachelor's degree in mathematics from the California Institute of Technology in 1969. At Stanford University, he received his Master's degree in computer science in 1971 and a Ph.D. in computer science (with a minor in mathematics) in 1972. At Stanford, he was supervised by Robert Floyd and Donald Knuth, both highly prominent computer scientists. His Ph.D. dissertation was An Efficient Planarity Algorithm, and his advisor was eminent computer scientist Robert Floyd.[2] Tarjan selected computer science as his area of interest, because he believed that CS was a way of doing mathematics that could have a practical impact.[3]

Computer science career

Tarjan has been teaching at Princeton University since 1985.[3] He has also held academic positions at Cornell University (1972-73), University of California, Berkeley (1973-1975), Stanford University (1974-1980), and New York University (1981-1985). He has also been a fellow of the NEC Research Institute (1989-1997), a Visiting Scientist at the Massachusetts Institute of Technology (1996).

Tarjan has vast industrial experience: he has worked at AT&T Bell Labs (1980-1989), InterTrust Technologies (1997-2001), Compaq (2002) and Hewlett Packard (2006-present). He has served on several ACM and IEEE committees, and has also been editor of several reputed journals.

Algorithms and data structures

Tarjan has designed many efficient algorithms and data structures for solving problems in a wide variety of application areas. He has published more than 228 refereed journal articles and book chapters.

Tarjan is known for his pioneering work on graph theory algorithms and data structures. Some of his well-known algorithms include the Tarjan's off-line least common ancestors algorithm, and the Tarjan's strongly connected components algorithm. The Hopcroft-Tarjan planarity testing algorithm was the first linear-time algorithm for planarity-testing.[4]

Tarjan has also developed important data structures such as the Fibonacci heap (a heap data structure consisting of a forest of trees), and the splay tree (a self-adjusting binary search tree; co-invented by Tarjan and Daniel Sleator). Another significant contribution was the analysis of the disjoint-set data structure; he was the first to prove the optimal runtime involving the inverse Ackermann function.

Tarjan is currently the James S. McDonnell Distinguished University Professor of Computer Science at Princeton University, and also works for Hewlett-Packard.[5]


Tarjan received the Turing Award jointly with John Hopcroft in 1986. The citation for the award states that it was:

For fundamental achievements in the design and analysis of algorithms and data structures.

Tarjan was also elected an ACM Fellow in 1994. The citation for this award [1] states:

For seminal advances in the design and analysis of data structures and algorithms.

Some of the other awards for Tarjan include:


  1. ^ a b Shasha, Dennis Elliott; Lazere, Cathy A. (1998) [1995]. "Robert E. Tarjan: In Search of Good Structure". Out of Their Minds: The Lives and Discoveries of 15 Great Computer Scientists. Copernicus/Springer. p. 102–119. ISBN 978-0387979922. OCLC 32240355.  
  2. ^ "Robert Endre Tarjan". Mathematics Genealogy Project. Retrieved 2008-01-09.  
  3. ^ a b "Robert Endre Tarjan: The art of the algorithm (interview)". Hewlett-Packard. September 2004. Retrieved 2008-01-09.  
  4. ^ Kocay, William; Kreher, Donald L (2005). "Planar Graphs". Graphs, algorithms, and optimization. Boca Raton: Chapman & Hall/CRC. p. 312. ISBN 978-1584883968. OCLC 56319851.  
  5. ^ "HP Fellows: Robert Endre Tarjan". Hewlett-Packard. Retrieved 2008-01-09.  


  • Tarjan, Robert E. (1983). Data structures and network algorithms. Philadelphia: Society for Industrial and Applied Mathematics. ISBN 978-0898711875. OCLC 10120539.  
  • Tarjan, Robert E.; Polya, George; Woods, Donald R (1983). Notes on introductory combinatorics. Boston: Birkhauser. ISBN 978-0817631703. OCLC 10018128.  
  • OCLC entries for Robert E Tarjan
  • DBLP entry for Robert Endre Tarjan

External links

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