- published: 21 Apr 2016
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In computer science, A* (pronounced "A star" (listen)) is a computer algorithm that is widely used in pathfinding and graph traversal, the process of plotting an efficiently traversable path between points, called nodes. Noted for its performance and accuracy, it enjoys widespread use. Peter Hart, Nils Nilsson and Bertram Raphael of Stanford Research Institute (now SRI International) first described the algorithm in 1968. It is an extension of Edsger Dijkstra's 1959 algorithm. A* achieves better performance (with respect to time) by using heuristics.
A* uses a best-first search and finds a least-cost path from a given initial node to one goal node (out of one or more possible goals).
It uses a distance-plus-cost heuristic function (usually denoted Failed to parse (Missing texvc executable; please see math/README to configure.): f(x) ) to determine the order in which the search visits nodes in the tree. The distance-plus-cost heuristic is a sum of two functions:
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The Failed to parse (Missing texvc executable; please see math/README to configure.): h(x)
Demetria Devonne "Demi" Lovato (born August 20, 1992) is an American singer-songwriter, musician, and actress. Her earliest roles included Angela on Barney & Friends, before she became better known for her starring roles in the Camp Rock movies, as Sonny Munroe in the Disney sitcom Sonny with a Chance, and as the star of the 2009 movie Princess Protection Program. She is also involved in philanthropic activities through charity work and various social and environmental causes.
As a solo musical artist, Lovato released her debut album Don't Forget on September 23, 2008. The album debuted at number two on the Billboard 200 selling 89,000 copies in the first week. It has since shipped over 500,000 copies, earning a gold certification in the United States. Lovato released her second album, Here We Go Again, on July 21, 2009. The album debuted at number one on the Billboard 200, selling 108,000 copies in the first week. Her third studio album, Unbroken, was released on September 20, 2011 and peaked at number four on the Billboard 200. She is working on her fourth studio album.