Practice Questions (Code Writing)
Loops
Table of contents
CodeCheck Questions
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Your task is to write a method getVowels that gets the vowels in a string. For example, the call getVowels(“Hello, World!”) should return the string “eoo”.
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Your task is to write a method evenSum that computes the sum of all even numbers between two given numbers. For example, the call evenSum(3, 8) should return 4 + 6 + 8 = 18.
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Given a number x, complete the program below named Power that computes the value of xn, where n is an integer. While the value of the double variable x can be positive or negative, the value of the integer n should be non-negative.
Input: x, the value to be raised to the nth power.
Input: n, the value of the power.
Output: xn, the value of x raised to the nth power. -
Given a positive number n, the factorial of that number, denoted n!, is equal to 1 x 2 x … (n - 1) x n. Assuming that n is greater than zero and less than 12, complete the program named Factorial below, so that it computes the value of n! for any positive n less than 12.
Input: n, the integer value for which n! is to be computed.
Output: n! – the factorial of n -
Your task is to write a method stutter that repeats all letters t in a string. For example, the call stutter(“stutter”) should return “sttutttter”.
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Your task is to write a method countSevens that counts the number of digits equal to 7 in a given number. For example, the call countSevens(1797) should return 2 since the number contains two digits 7.
Hint: Repeatedly compute % 10 and / 10.
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Complete the ReverseString program below so that it reads in a string of characters, reverses the order of the characters, and prints out the reversed string.
In other words, if the input string is “123456”, the output string would be “654321”.
If the input string is “How now, brown cow”, the output string would be “woc nworb ,won woH”. -
When people enter their telephone numbers into a form they use many different formats. Some examples are:
(444) 999-1234
4449991234
444.999.1234
In thePhoneNumbersclass below, complete thecleanNumbermethod. It takes a string and extracts the numeric digits from the string. If there are exactly 10 numeric digits, the number is reformatted:(###) ###-####and returned. If there are any other number of digits, the string “Error” is returned.
Hint: Use theCharacter.isDigitmethod to check whether a character is a digit.
Medium CodeCheck Questions
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Your task is to write a method countPerfectSquares that counts all perfect squares in a given range. For example, the call countPerfectSquares(5, 25) should return 3 (since 9, 16, and 25 are perfect squares between 5 and 25).
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A palindrome is a string that is the same spelled forward as it is spelled backward. So, “abcba” is a palindrome, as are “eye” and “madam”.
Complete the PalFind program below so that it reads in a string of characters, checks character-by-character to see whether or not the string is a palindrome, and then prints either “Yes” or “No”.
In other words, if the input string is “abba” or “wallow”, the output would be “Yes”. If the input string is “FBI” or “garbage”, the output would be “No”.
You may ignore punctuation, in that the test strings used for this program do not contain any. You may also modify the whole string to all uppercase or all lowercase before you begin the check.
Note: The strings may be of odd or even length, as in “cat”, “dad”, “racecar”, or “Hannah”. -
A simple technique for compressing an image is run-length encoding. The color of each pixel or area is specified for an image. The color pallette can be specified by the first letter of each color (R, G, B, C, M, Y, K, W) - red, green, blue, cyan, magenta, yellow, black, white. An example 6 by 4 image is:
RRRGGGYYYYWBWWRGBBBBBRRR
Run-length encoding counts the number of each color in a group and replaces the individual color values by a number and the color. For our example, this would give:
3R3G4Y1W1B2W1R1G5B3R
Complete the compressImage method to run-length compress a string of characters.