Lars Erik Petrus (born 4 November 1960 in

Luleå Luleå ( , , locally ; smj, Luleju; fi, Luulaja) is a city on the coast of northern Sweden, and the capital of Norrbotten County, the northernmost county in Sweden. Luleå has 48,728 inhabitants in its urban core (2018) and is the seat of Lu ...

in Sweden) is an accomplished

speedcuber Speedcubing (also known as speedsolving, or cubing) is a competitive sport involving solving a variety of combination puzzles, the most famous being the 3x3x3 puzzle or Rubik's Cube, as quickly as possible. An individual who practices solving tw ...

. In 1982, he became the national champion of

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic countries, Nordic c ...

, and went on to finish fourth overall at the first official

Rubik's Cube The Rubik's Cube is a Three-dimensional space, 3-D combination puzzle originally invented in 1974 by Hungarians, Hungarian sculptor and professor of architecture Ernő Rubik. Originally called the Magic Cube, the puzzle was licensed by Rubik t ...

World Championships held in

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. He later published his method, known as the Petrus system, on the Internet. It became a fairly popular method among intermediate and upper-level speedcubers, although its more recent use has diminished considerably due to the increased predominance of methods such as ZZ, Roux, and CFOP. Petrus won the 3x3x3 Fewest Moves category at the 2005 World Championships held in November 2005 at

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, USA claiming the US$500 prize. He currently (since 1995) resides in SF Bay Area,

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, USA.

The Lars Petrus System

The Petrus System was designed as an alternative to the popular layer-based solutions of the early 1980s. Petrus reasoned that as a solver constructs layers, further organization of the cube's remaining pieces is restricted by what one has already done. In order for a layer-based solution to continue after the first layer had been constructed, the solved portion of the cube would have to be temporarily disassembled while the desired moves were made, then reassembled afterward. Petrus sought to get around this by solving the cube outwards from one corner, leaving him with unrestricted movement on several sides of the cube as he progressed. This method is often used to solve the cube in a fewest-moves solution.

The Method

The system uses seven basic steps to solve a Rubik's Cube. # Build a 2x2x2 block # Expand to a 2x2x3 without destroying the 2x2x2 block # Correct edge orientation (EO) # Solve two complete layers # Permute the remaining corners (CP) # Orient the remaining corners (CO) # Permute the final edges (EP) Petrus invented three simple and flexible algorithms to complete the last three steps, which he named Niklas, Sune, and Allan. While the method stands alone as an efficient system for solving the Rubik's Cube, many modifications have been made over the years to stay on the cutting edge of competitive speedcubing. Many more algorithms have been added to shave seconds off the solution time, and steps 5+6 or 6+7 are often combined depending on the problems each case presents.

External links

Rubik's World Championship 2005
- Official Results
Solving Rubik's Cube for Speed
by Lars Petrus
Lars's Official Records
- From the

World Cube Association The World Cube Association (WCA) is the worldwide non-profit organization that regulates and holds competitions for mechanical puzzles that are operated by twisting groups of pieces, commonly known as '' twisty puzzles'' (a subcategory of combin ...

website {{DEFAULTSORT:Petrus, Lars Swedish speedcubers 1960 births Living people Google employees People from Luleå Sportspeople from Norrbotten County sv:Rubiks kub#Petrus-metoden