Introduction to Computers

-Final exam-授課教授：李錫智

Q1

• Write a function named Reverse that takes a string as input and returns a copy of that string in reverse order. For example, the function call Reverse("apple") should return the string "elppa".

Solution of Q1

• Ans:

function Reverse(str)

{

var len,restr;

len=str.length;

restr="";

i=len-1;

while(i!=-1)

{

restr=restr+str.charAt(i);

i=i-1;

}

}

Q2

• Consider the following program :function string(string){

str = string;i = str.search(/[aeiou]/);while(i != -1){

str = str.substring(0,i) + '*' + str.substring(i+1,str.length);

i = str.search(/[aeiou]/);}return str;

}

• What will be returned for the function call string('Hello world')?

Solution of Q2

• Ans: H*ll* w*rld

Q3

• Write a function named Maximum that takes an array of numbers as input and return the biggest value in the array. For example, the call Maximum([2, 28, 33, 12, 5, 17, 8]) should return 33.

Solution of Q3

Q4

• Suppose you are given the following segment of program:

Phrase = “George Bush, USA\n”+“Leonardo da Vinci, Italy\n”+“William Shakespeare, England\n”;Spilt_1 = Phrase.split(“, “);Spilt_2 = Phrase.split(/[,\n]+/);

• [5] What is the value of Split_1?

• [5] What is the value of Split_2?

Solution of Q4

• Ans:• Split_1 = ["George Bush", "USA\nLeonardo da Vinci",

"Italy\nWilliam Shakespeare", "England\n"] ;• Split_2 = ["George Bush", "USA", "Leonardo da Vinci",

"Italy", "William Shakespeare", "England"];

Q5

• Please using the NOT, AND, and OR gates, draw a circuit that will output 0 while both inputs are 0 or 1. That is, suppose A and B are the two inputs and C is the output, then C=0 if and only if (A=0 and B=0) or (A=1 and B=1).

Solution of Q4

A B C

0 0 0

0 1 1

1 0 1

1 1 0

Q6• Consider the following program:

• What will be returned for the function call Cipher('Bronze')?

function Cipher(str){

var coded, ch, index, key, i;alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';coded = ' ';key = 4;str = str.toUpperCase();i = 0;while(i < str.length){

ch = str.charAt(i);index = alphabet.search(ch);if (index != -1) {

if ( (index+key) < alphabet.length) {coded = coded + alphabet.charAt(index+key);

}else {coded = coded + alphabet.charAt(index+key-alphabet.length);

}}else {

coded = coded + ch;}i = i + 1;

}return coded;

}

Solution of Q6

• Ans: FVSRDI

Offset 4 characters.

Q7

• Suppose you are given an array of numbers, A.

• (a) [10] Please write a function taking A and returning an array B which records the number of times each element appearing in A. For example, suppose A=[15,25,35,45,35,35,25]. Then B=[1,2,3,1,3,3,2].

• (b) [10] Please write a function taking A and returning the element in A which appears most frequently in A. For example, for the above example, 35 will be returned.

Solution of Q7

Q8

• Please design a Web page that asks the user to enter his/her name and age in a phrase separated by a colon, e.g., John :36.

• When the user clicks a button, the webpage will show the name and say the user is an adult or a child, e.g., John is an adult.

• Note that a person is an adult if his/her age is equal to or greater than 20.

Solution of Q8

Q9

• Consider the following circuit. A, B, and C are inputs. P and Q are outputs. Please list the input-output relationship in a truth table.

Solution of Q9

A B C Q P

0 0 0 0 0

0 0 1 0 1

0 1 0 0 1

0 1 1 1 0

1 0 0 0 1

1 0 1 1 0

1 1 0 1 0

1 1 1 1 1

Q10

• Please write a function to check whether a given string is a mirror-string. A string A is a mirror-string if and only if A satisfies one of the following conditions:• A is a concatenation of B and C, i.e., A=BC, where B

and C are strings and C is the reverse of B. For example, “abccba” is a mirror-string.• A is a concatenation of B, t, and C, i.e., A=BtC, where B

and C are strings, t is a character, and C is the reverse of B. For example, “abcycba” is a mirror-string.

Solution of Q10

• Ans :

function IsP(string) {

var stripped, front, back;

stripped = string;

front = 0;

back = stripped.length - 1;

while (front < back) {

if (stripped.charAt(front) != stripped.charAt(back)) {

return false;

}

front = front + 1;

back = back - 1;

}

return true;

}

The end of the final Exam