NDFA where 3 symbol from right end is a

Duration: 5 min

This video lesson is available to enrolled students.

Return to /learn/IBPS-SO-IT-PRELIMS/theory-of-computation/non-deterministic-fa/nfa-basics-design/asset-ndfa-where-3-symbol-from-right-end-is-a after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. English Language: Vocabulary, Noun, Adjectives, Tenses, Pronoun, Adverb, Preposition, Conjunction, Active Passive Voice (Voice), Articles, Direct and Indirect Speech, Sentence Correction (Error Correction), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Completion (Fill in the blanks), Cloze Test (Cloze Passage)
  3. Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Puzzle Solving (Puzzles), Seating Arrangements, Blood Relations, Syllogisms, Inequality, Directions (Direction Test), Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Clock, Calendar, Analytical Reasoning (Counting Figures Reasoning), Selection Decision Table (Decision Making), Cubes & Dices, Machine Input-Output
  4. Quantitative Aptitude: Ratio and Proportion (Ratios), Data Interpretation, Mixture and Alligation, Permutation and Combination, Number System, Sequence and Series (Series), Speed Time and Distance, Algebra, Speed Mathematics and Basic Mathematics, Percentage, Average, Time and Work, Simple Interest and Compound Interest, Profit and Loss, Age Problems, Partnership, Mensuration and Geometry, Probability, IBPS Specific Videos
  5. Data Structures - Professional Knowledge: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  6. Algorithms- Professional Knowledge: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  7. Python- Professional Knowledge: Python for Placements by Yash Sir, Python Basics
  8. Operating System- Professional Knowledge: Introduction to OS, Process Management, CPU Scheduling, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management
  9. DBMS + SQL- Professional Knowledge: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), File Organization & Indexing, SQL, Transaction Management, Concurrency Control
  10. Computer Networks- Professional Knowledge: Introduction to CN, Data Communication, Net Layer: IP Addressing, Net Layer: IPv4 & Proto, Application Layer, Hardware basics, Network Security
  11. Software Engineering- Professional Knowledge: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  12. Computer Organization & Microprocessor- Professional Knowledge: Basics of COA, Cache Memory Organization, Programming the Basic Computer
  13. Digital Logic Design- Professional Knowledge: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  14. Theory of Computation- Professional Knowledge: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Regular Language Properties, Pushdown Automata & CFG, Turing Machines
  15. Compiler Design- Professional Knowledge: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Intermediate Code Gen, Code Optimization
  16. Programming Languages- Professional Knowledge: C Programming by Yash Sir, Object Oriented Programming (OOPS), Programming in C++, Java, C Language Core
  17. Emerging Tech- Professional Knowledge: Emerging Tech Trends
  18. Artificial Intelligence: Artificial Intelligence
  19. Unit Test - Professional Knowledge:
  20. Full Length Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video presents an educational lecture on automata theory, focusing on the design of an NDFA. The core problem displayed is: "Design a NDFA that accepts all strings over the alphabet $\Sigma = \{a, b\}$ such that for every accepted string 3rd from right end is always a." The instructor begins by analyzing the problem requirements. He starts by drawing a preliminary state diagram on the top left quadrant. This initial attempt involves a sequence of states $q_0, q_1, q_2$ where transitions are labeled with input symbols. He quickly modifies this by adding a transition from $q_1$ to a new state $q_3$ with a self-loop, suggesting an exploration of how to handle different input characters at specific positions.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with the problem statement. The instructor begins drawing the first NDFA attempt. He draws a circle for state $q_0$ with an incoming arrow indicating the start. He draws a transition to state $q_1$ labeled "$a, b$". From $q_1$, he draws a transition to state $q_2$ labeled "$b$" and marks $q_2$ with a double circle to indicate it is an accepting state. He then adds a transition from $q_1$ to a new state $q_3$ labeled "$a$" and draws a self-loop on $q_3$ labeled "$a, b$". He writes "x b x x x" below this diagram, likely testing a string where 'b' is at the 3rd position from the right to see if it gets rejected or accepted.

  2. 2:00 – 5:00 02:00-05:00

    The instructor moves to the top right quadrant to draw a second attempt. He draws states $q_0, q_1, q_2$ in a line. Transitions are $q_0 \xrightarrow{a,b} q_1$ and $q_1 \xrightarrow{b} q_2$ (accepting). He writes "x b x x x" again. Then, he moves to the bottom left to draw a more complex graph. He draws a self-loop on $q_0$ labeled "$a$". He then moves to the bottom right to draw the final, most refined diagram. This diagram shows $q_0$ with a self-loop labeled "$a, b$". From $q_0$, there is a transition to $q_1$ labeled "$b$". From $q_1$, a transition to $q_2$ labeled "$a, b$". From $q_2$, a transition to $q_3$ (accepting) labeled "$a$". He writes "x x x b - -" below this, possibly indicating a string ending in 'b' at the 3rd position which should be rejected.

  3. 5:00 – 5:10 05:00-05:10

    The video ends with the instructor pointing at the final diagram on the bottom right. He gestures towards the transitions, specifically the path from $q_0$ through $q_1, q_2$ to the accepting state $q_3$. The diagram represents the logic of guessing the position of the 'a' character from the right. The self-loop on $q_0$ allows the machine to consume any prefix before the critical 'a'. The subsequent chain of states ensures that exactly two characters follow the guessed 'a' before reaching the accepting state.

The lecture demonstrates the iterative process of automata design. The instructor shows the trial-and-error phase, drawing multiple diagrams to explore transition logic. He uses example strings on the board to validate state transitions. The progression from a simple linear chain to a diagram with self-loops highlights the key concept of NDFA: the ability to guess the correct path. The final diagram encapsulates the standard solution for "k-th from right" problems, where the machine non-deterministically guesses the target character and verifies the suffix length.

Loading lesson…