It is a flexible notation that can be adjusted to fit your own view about how best to express ideas and algorithms. Under what circumstances would the body of a pretest loop never be executed? ANSWER: With a pretest loop, the continuation condition is tested at the beginning of each pass through the loop, and therefore it is possible for the loop body never to be executed. This would happen if the continuation condition were initially false.
Briefly define the concept of iteration ANSWER: The powerful algorithmic concept of iteration means that instead of writing instruction 10, separate times, it is far better to write it only once and indicate that it is to be repetitively executed 10, times, or however many times it takes to obtain the answer.
What is the definition of a library in terms of algorithms? ANSWER: In the world of algorithms, a library is a collection of useful, prewritten algorithms, which are an important tool in the design and development of algorithms. What is pattern matching? ANSWER: Pattern matching is the process of searching for a special pattern of symbols within a larger collection of information. What is the problem with using natural language to represent algorithms?
ANSWER: Natural language can be extremely verbose, causing the resulting algorithms to be rambling, unstructured, and hard to follow. The lack of structure makes it difficult for the reader to locate specific sections of the algorithm because they are buried inside the text.
For example, without any clues to guide us, such as indentation, line numbering, or highlighting, locating the beginning of a loop can be a daunting and time-consuming task. This permits different readers to interpret the same sentence in totally different ways. This may be acceptable, even desirable, when writing poetry or fiction, but it is disastrous when creating algorithms that must always execute in the same way and produce identical results.
What is the problem with using high-level programming languages to represent algorithms? During the initial phases of design, we should be thinking and writing at a highly abstract level. Using a programming language to express our design forces us to deal immediately with detailed language issues, such as punctuation, grammar, and syntax. These technical details clutter our thoughts and at this point in the solution process are totally out of place. When creating algorithms, a programmer should no more worry about semicolons and capitalization than a novelist should worry about typography and cover design when writing the first draft.
What is pseudocode and why is it well-suited for representing algorithms? This is a set of English language constructs designed to resemble statements in a programming language but that do not actually run on a computer. Pseudocode represents a compromise between the two extremes of natural and formal languages. It is simple, highly readable, and has virtually no grammatical rules. In fact, pseudocode is sometimes called a programming language without the details.
However, because it contains only statements that have a well-defined structure, it is easier to visualize the organization of a pseudocode algorithm than one represented as long, rambling natural-language paragraphs.
In addition, because pseudocode closely resembles many popular programming languages, the subsequent translation of the algorithm into a computer program is relatively simple.
Pseudocode is not a formal language with rigidly standardized syntactic and semantic rules and regulations. On the contrary, it is an informal design notation used solely to express algorithms. One of the nice features of pseudocode is that you can adapt it to your own personal way of thinking and problem solving.
Explain the importance of the concept of building blocks in the use of algorithms. You might think that every algorithm you write must be built from only the most elementary and basic of primitives.
However, once an algorithm has been developed, it may itself be used in the construction of other, more complex algorithms. This is similar to what a builder does when constructing a home from prefabricated units rather than bricks and boards. Our problem-solving task need not always begin at the beginning but can instead build on ideas and results that have come before. Every algorithm that we create becomes, in a sense, a primitive operation of our computing agent and can be used as part of the solution to other problems.
That is why a collection of useful, prewritten algorithms, called a library, is such an important tool in the design and development of algorithms. Discuss in detail the application of pattern matching to the mapping of the human genome. ANSWER: One of the most interesting and exciting applications of pattern matching is assisting microbiologists and geneticists studying and mapping the human genome, the basis for all human life.
The human genome is composed of a sequence of approximately 3. These compounds adenine, cytosine, thymine, guanine are usually referred to by the first letter of their chemical names: A, C, T, and G. There are about 25, genes in the human genome, and they determine virtually all of our physical characteristics— sex, race, eye color, hair color, and height, to name just a few.
Genes are also an important factor in the occurrence of certain diseases. A missing or flawed nucleotide can result in one of a number of serious genetic disorders, such as Down syndrome or Tay-Sachs disease.
To help find a cure for these diseases, researchers are attempting to locate individual genes that, when exhibiting a certain defect, cause a specific malady. A gene is typically composed of thousands of nucleotides, and researchers generally do not know the entire sequence. However, they may know what a small portion of the gene—say, a few hundred nucleotides— looks like.
Therefore, to search for one particular gene, they must match the sequence of nucleotides that they do know, called a probe, against the entire 3. From this matching information, researchers hope to isolate specific genes. When a match is found, researchers examine the nucleotides located before and after the probe to see whether they have located the desired gene and, if so, to see whether the gene is defective.
There is no one correct answer. Common examples are the instructions for using a voice mail system, the instructions for opening a mail box lock, and the instructions for doing laundry. Heuristics are often used when executing an algorithm might be too timeconsuming, and we only need an approximation to the correct answer.
Set the one and tens digit of both operands to 0 2. Increase the hundreds digit of the second operand by 1. Now, of course, this is not the correct answer, which is But the result we get may be close enough for our needs, and it is certainly a lot easier to add a single column of numbers rather than three columns of numbers. One may argue that the instruction is not well-ordered, since it is unclear whether one should enter the channel first or press CHAN first.
Add an operation at the beginning of the algorithm that resets the two numbers to the same number of digits by adding non-significant leading zeros to the shorter one. We can then reuse the algorithm of Figure 1. All we need do now is set the variable m to the larger of the two values: Set m to the larger of m and n. The addition algorithm in Figure 1. Note that if m and n are equal in value, neither of the Boolean expressions will be true, and neither of the conditional statements will be executed.
The first algorithm Figure 1. If you want to shampoo your hair any number n times you can change the 2 to n. You could even ask the shampooer to input the desired number n of washings. For the second algorithm you would have to rewrite the algorithm to repeat steps 4 and 5 more times. There are 25! That is approximately 1. The computer can analyze 10,,, or , paths per second. The number of seconds required to check all possible paths is about 1.
This would not be a feasible algorithm. A Multiplication Algorithm. Given: Two positive numbers a and b Wanted: A number c which contains the result of multiplying a and b Step 1: Set the value of c equal to 0 Step 2: Set the value of i equal to b Step 3: Repeat steps 4 and 5 until the value of i is 0.
Step 6: Print out the final answer c Step 7: Stop This algorithm assumes that we know how to add two multiple-digit numbers together. We may assume this because we have the algorithm from the book which does exactly that. The algorithm will work correctly only if all three numbers are unique.
If two or more numbers are identical, none of the Boolean expressions will be true and nothing will be output. This is an essay question. Students may find excellent resources on the Internet. If this problem is assigned, be sure to coordinate with your computing staff ahead of time for students to get the required information. It might be a good opportunity to teach students about finding reliable sources on the Internet, and evaluating online and print source materials.
Like question 16 this is an essay question. Students may be familiar with Apple iCloud services for iPhone and iPad devices, so it might be a good opportunity to relate their answers to the services provided by Apple.
We may perform subtraction, like addition, by subtracting one column at a time, starting with the rightmost column and working to the left. Since we know that the first number is larger than the second one, we know that we can always borrow from columns to the left of the current one. If You feel that this book is belong to you and you want to unpublish it, Please Contact us. Invitation to Computer Science 7th Edition. Download e-Book. Posted on. Page Count. Download e-Book Pdf.
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