Wiktionary
n. The act of one who, or that which, backtracks; a retracing of one's steps. vb. (present participle of backtrack English)
Wikipedia
Backtracking is a general algorithm for finding all (or some) solutions to some computational problems, notably constraint satisfaction problems, that incrementally builds candidates to the solutions, and abandons each partial candidate c ("backtracks") as soon as it determines that c cannot possibly be completed to a valid solution.
The classic textbook example of the use of backtracking is the eight queens puzzle, that asks for all arrangements of eight chess queens on a standard chessboard so that no queen attacks any other. In the common backtracking approach, the partial candidates are arrangements of k queens in the first k rows of the board, all in different rows and columns. Any partial solution that contains two mutually attacking queens can be abandoned.
Backtracking can be applied only for problems which admit the concept of a "partial candidate solution" and a relatively quick test of whether it can possibly be completed to a valid solution. It is useless, for example, for locating a given value in an unordered table. When it is applicable, however, backtracking is often much faster than brute force enumeration of all complete candidates, since it can eliminate a large number of candidates with a single test.
Backtracking is an important tool for solving constraint satisfaction problems, such as crosswords, verbal arithmetic, Sudoku, and many other puzzles. It is often the most convenient (if not the most efficient) technique for parsing, for the knapsack problem and other combinatorial optimization problems. It is also the basis of the so-called logic programming languages such as Icon, Planner and Prolog.
Backtracking depends on user-given " black box procedures" that define the problem to be solved, the nature of the partial candidates, and how they are extended into complete candidates. It is therefore a metaheuristic rather than a specific algorithm – although, unlike many other meta-heuristics, it is guaranteed to find all solutions to a finite problem in a bounded amount of time.
The term "backtrack" was coined by American mathematician D. H. Lehmer in the 1950s. The pioneer string-processing language SNOBOL (1962) may have been the first to provide a built-in general backtracking facility.
Usage examples of "backtracking".
As the backtracking train squealed to a stop dozens of doors opened and crowds of people jumped out to see what had happened.
If Sanner was backtracking, that meant he intended to confer with the rest of the rescue team and perhaps make them retrace their steps.
Even so, the thought of backtracking gnawed at him as they approached the entrance to the final chamber.
Maybe it was all the practice tracking and backtracking through the cave system.
Stanton had to engage in furious backtracking, growing connective tissue to the pro-slavery radicals through that foppish Massachusetts Senator, Sumner.
Kirk, backtracking, ducked behind a large machine and pulled out his phaser.
Our route was circuitous in the extreme, full of loops, detours and backtrackings.
But the direction of that hunting was a challenge in itself, and she was certain that in all his twists and turnings and backtrackings, he made sure he rode toward the broken land that bordered directly on the Bog.
With frequent halts and backtrackings, and carefully omitting any mention of his tumblings with Calissa, he told Ludya of the events that had unfolded after her exile from the Manse.
In the end it was decided that sufficient other safeguards had been put in place for the Displacements to go ahead, with the aim of backtracking along the attempted wormhole link to discover and even attack the Involveds behind the attack (this failed and to the best of my knowledge it is still not known who those mysterious allies were, though I’m sure SC has its suspicions).
She stumbled on, following the current, backtracking the gentle breeze.
It lacked the imperfect recall, the fuzziness, the additions and subtractions dictated by wishful thinking and self-interest, to say nothing of the lingerings and lacunae and backtracking that can turn memory into hours-long daydreaming.
He refiled the altered spool and did a little backtracking, shifting the last report of Sam Hall from Salt Lake City to Atlanta.
Sirhan can feel her unease, the tenuous grasping of her ghosts as she searches for reason in an unreasonable world, simulating outcomes, living through bad dreams, and backtracking to adjust her responses accordingly.
Nowadays one can follow the trail, and minimize the ups and down, end-runs, dead-ends, and backtracking necessary to make one's way in any direction.