Reverse of a string
Duration: 1 min
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- General Intelligence & Reasoning: Analogy, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Logical Sequence Of Words, Syllogisms, Venn Diagram, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Data Sufficiency, Puzzle Solving (Puzzles), Data Arrangement, Cubes & Dices, Calendar, Clock, Arithmetic, Number System, HCF LCM, Verbal Analogy (Word Based Analogy), Visual Recognition and Figure Completion, Paper Folding and Cutting, Transformation of Shapes, Clocks and Calendars, Direction Sense, Cubes and Dice, Patterns in Two-Dimensional Figures, Seating Arrangements, Analogy and Classification, Logical Deduction and Induction, Alphabet and Word Tests, Mathematical Operations, Series Completion, Simplification and Approximation, Coding and Decoding, Numerical Reasoning, Assembling and Grouping of Shapes, Three-Dimensional Patterns and Visualization, Vocabulary, Number System, Averages, Mixtures and Alligation, Simple and Compound Interest, Percentages, Algebra, Speed, Time and Distance, Seating and Arrangement Puzzles, Traverse Surveying, Order, Ranking and Sequence, Constraint Puzzles, Syllogisms and Venn Diagrams, Reading Comprehension, Critical Reasoning, Permutations and Combinations, Narrative Sequencing, Project Monitoring, Resources and Safety, Profit, Loss and Discount, Ratio and Proportion, Time and Work, Mensuration, Data Interpretation, Powers, Surds and Logarithms, Sequences and Series, Articles and Determiners, Sentence Completion, Data Sufficiency, Blood Relations, Simple Interest and Compound Interest, Mixture and Alligation, Sequence and Series (Series), Speed Time and Distance, Algebra, Profit and Loss, Powers and Exponents (Surds and Indices), Permutation and Combination
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- Full Length Mock Tests:
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AI summary & chapters
AI Summary
An AI-generated summary of this video lecture.
This educational segment focuses on the fundamental operation of reversing a string within the context of formal languages and automata theory. The instructor begins by defining a generic string W composed of a sequence of symbols w1, w2, w3, ..., wn. The reverse of this string, denoted by the notation Wr, is explicitly defined as the sequence of these same symbols arranged in reverse order, specifically wn, wn-1, ..., w1. To illustrate this concept, a specific example is written on the screen: the string W = abbc. The instructor demonstrates that reversing this string results in Wr = cbba. A crucial property is then introduced: the length of a string is equal to the length of its reverse, mathematically expressed as |w| = |wr|. The lecture concludes by briefly introducing the concept of the Empty or Null String, denoted by epsilon, noting that its length is zero (|epsilon|=0), and defining string powers where wn represents the string w repeated n times, such as w3 = www. This foundational knowledge is critical for understanding more complex string manipulations in computer science and engineering.
Chapters
0:00 – 1:08 00:00-01:08
The video defines string reversal starting with the notation W = w1w2...wn. It shows the reverse Wr = wn...w1 and uses the example abbc becoming cbba. The property |w| = |wr| is written. Finally, the slide changes to "Empty/Null String" defining epsilon and powers like w3 = www. The instructor explains that w0 is the empty string and w epsilon = epsilon w = w. This sequence of definitions establishes the basic algebraic properties of strings and their operations.
The lecture systematically builds the concept of string reversal from definition to application. By establishing the notation Wr and proving the length invariance |w| = |wr|, the instructor provides a clear mathematical foundation. The transition to null strings and powers suggests a broader context of string operations is being covered in the full course. Understanding these basic operations is essential for analyzing formal languages effectively. These concepts form the bedrock of theoretical computer science and related fields.

