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assignment 2 #2

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118 changes: 118 additions & 0 deletions Assignment2/Main.java
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import java.util.Scanner;
import mypackage.Operations;


public class Main {

public static void main(String[] args) {
Scanner input = new Scanner(System.in);
Operations ops = new Operations(); // Create an instance of Operations class

while (true) {
// Display the menu
System.out.println("\n---- MENU: STRING & NUMBER OPERATIONS ----\n");
System.out.println("1. Count Unique Palindromic Substrings");
System.out.println("2. Nth Fibonacci Number");
System.out.println("3. Convert Snake Case to Camel Case");
System.out.println("4. Count Consonants in a String");
System.out.println("5. Binary to Decimal Conversion");
System.out.println("6. Expand Characters Based on Digits (e.g. a1b2 → abb)");
System.out.println("7. Character Frequency in a String");
System.out.println("8. Prime Number Checker");
System.out.println("9. Convert Number to Words");
System.out.println("10. Longest Substring Without Repeating Characters");
System.out.println("0. Exit");
System.out.print("Enter your choice: ");

int choice = input.nextInt();
input.nextLine(); // consume newline character

switch (choice) {
// Exit program
case 0:
System.out.println("Exiting program... Thank you!");
input.close();
return;

// 1. Count Unique Palindromic Substrings
case 1:
System.out.print("Enter a string: ");
String palindromeInput = input.nextLine();
int palindromeCount = ops.countUniquePalindromes(palindromeInput);
System.out.println("Unique palindromic substrings: " + palindromeCount);
break;

// 2. Nth Fibonacci Number
case 2:
System.out.print("Enter N: ");
int n = input.nextInt();
System.out.println("Nth Fibonacci number: " + ops.getNthFibonacci(n));
break;

// 3. Convert Snake Case to Camel Case
case 3:
System.out.print("Enter a snake_case string: ");
String snakeCase = input.nextLine();
System.out.println("CamelCase: " + Operations.snakeToCamel(snakeCase));
break;

// 4. Count Consonants in a String
case 4:
System.out.print("Enter a string: ");
String consonantInput = input.nextLine();
int consonantCount = Operations.countConsonants(consonantInput);
System.out.println("Number of consonants: " + consonantCount);
break;

// 5. Binary to Decimal Conversion
case 5:
System.out.print("Enter a binary string: ");
String binary = input.nextLine();
int decimal = Operations.binaryToDecimal(binary);
System.out.println("Decimal equivalent: " + decimal);
break;

// 6. Expand Characters Based on Digits
case 6:
System.out.print("Enter string with characters followed by digits (e.g. a1b2c3): ");
String expandInput = input.nextLine();
System.out.println("Expanded string: " + Operations.expandCharacters(expandInput));
break;

// 7. Character Frequency in a String
case 7:
System.out.print("Enter a string: ");
String freqInput = input.nextLine();
System.out.println("Character frequency: " + Operations.charFrequency(freqInput));
break;

// 8. Prime Number Checker
case 8:
System.out.print("Enter a number: ");
int num = input.nextInt();
boolean prime = Operations.isPrime(num);
System.out.println(num + (prime ? " is PRIME" : " is NOT PRIME"));
break;

// 9. Convert Number to Words
case 9:
System.out.print("Enter a number: ");
int numWords = input.nextInt();
System.out.println("Number in words: " + Operations.numberToWords(numWords));
break;

// 10. Longest Substring Without Repeating Characters
case 10:
System.out.print("Enter a string: ");
String substringInput = input.nextLine();
int maxLength = Operations.longestUniqueSubstring(substringInput);
System.out.println("Length of longest substring without repeating characters: " + maxLength);
break;

// Invalid choice handling
default:
System.out.println("Invalid choice! Please try again.");
}
}
}
}
273 changes: 273 additions & 0 deletions Assignment2/mypackage/Operations.java
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package mypackage;

public class Operations {

// 1. Count unique palindromic substrings in a string
public int countUniquePalindromes(String str) {
String[] uniquePalindromes = new String[str.length() * str.length()];
int uniqueCount = 0;

for (int center = 0; center < str.length(); center++) {
// Odd-length palindromes
uniqueCount = expandAndStore(str, center, center, uniquePalindromes, uniqueCount);
// Even-length palindromes
uniqueCount = expandAndStore(str, center, center + 1, uniquePalindromes, uniqueCount);
}

return uniqueCount;
}

// Expand around center and store unique palindromes
private int expandAndStore(String str, int left, int right, String[] uniqueList, int count) {
while (left >= 0 && right < str.length() && str.charAt(left) == str.charAt(right)) {

String current = "";
for (int i = left; i <= right; i++) {
current += str.charAt(i);
}

boolean alreadyExists = false;
for (int i = 0; i < count; i++) {
if (isSame(uniqueList[i], current)) {
alreadyExists = true;
break;
}
}

if (!alreadyExists) {
uniqueList[count] = current;
count++;
}

left--;
right++;
}
return count;
}

// Compare two strings manually
private boolean isSame(String a, String b) {
if (a.length() != b.length()) return false;
for (int i = 0; i < a.length(); i++) {
if (a.charAt(i) != b.charAt(i)) return false;
}
return true;
}

// 2. Find the Nth number in the Fibonacci sequence
public int getNthFibonacci(int n) {
if (n == 1) return 0;
if (n == 2) return 1;

int first = 0, second = 1, next = 0;

for (int i = 3; i <= n; i++) {
next = first + second;
first = second;
second = next;
}

return next;
}

// 3. Convert snake_case to camelCase
public static String snakeToCamel(String snakeCaseString) {
String result = "";
boolean toUpper = false;

for (int i = 0; i < snakeCaseString.length(); i++) {
char ch = snakeCaseString.charAt(i);

if (ch == '_') {
toUpper = true;
} else {
if (toUpper && ch >= 'a' && ch <= 'z') {
ch = (char) (ch - 32); // convert to uppercase
}
result += ch;
toUpper = false;
}
}

return result;
}

// 4. Count consonants in a string
public static int countConsonants(String str) {
int consonantCount = 0;

for (int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);

if (ch >= 'A' && ch <= 'Z') {
ch = (char) (ch - 'A' + 'a'); // convert to lowercase
}

if (ch >= 'a' && ch <= 'z' &&
ch != 'a' && ch != 'e' && ch != 'i' && ch != 'o' && ch != 'u') {
consonantCount++;
}
}

return consonantCount;
}

// 5. Convert binary string to decimal (manual calculation)
public static int binaryToDecimal(String binaryString) {
int decimalValue = 0;
int base = 1;

for (int i = binaryString.length() - 1; i >= 0; i--) {
if (binaryString.charAt(i) == '1') {
decimalValue += base;
}
base *= 2;
}

return decimalValue;
}

// 6. Expand characters based on the digit following them
public static String expandCharacters(String str) {
String result = "";
int i = 0;

while (i < str.length()) {
char ch = str.charAt(i);

if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
i++;
int count = 0;

while (i < str.length() && str.charAt(i) >= '0' && str.charAt(i) <= '9') {
count = count * 10 + (str.charAt(i) - '0');
i++;
}

for (int j = 0; j < count; j++) {
result += ch;
}
} else {
i++;
}
}

return result;
}

// 7. Character frequency in a string (compressed form)
public static String charFrequency(String str) {
String result = "";
int n = str.length();

for (int i = 0; i < n; i++) {
char ch = str.charAt(i);
int count = 1;

// Skip already counted characters
boolean alreadyCounted = false;
for (int k = 0; k < i; k++) {
if (str.charAt(k) == ch) {
alreadyCounted = true;
break;
}
}
if (alreadyCounted) continue;

// Count occurrences
for (int j = i + 1; j < n; j++) {
if (str.charAt(j) == ch) count++;
}

result += ch + Integer.toString(count);
}

return result;
}

// 8. Prime number checker
public static boolean isPrime(int num) {
if (num <= 1) return false;

for (int i = 2; i * i <= num; i++) {
if (num % i == 0) return false;
}

return true;
}

// Arrays for number-to-words conversion
private static final String[] units = {
"zero", "one", "two", "three", "four",
"five", "six", "seven", "eight", "nine"
};

private static final String[] teens = {
"ten", "eleven", "twelve", "thirteen", "fourteen",
"fifteen", "sixteen", "seventeen", "eighteen", "nineteen"
};

private static final String[] tens = {
"", "", "twenty", "thirty", "forty",
"fifty", "sixty", "seventy", "eighty", "ninety"
};

// 9. Convert number to words
public static String numberToWords(int num) {
if (num < 0) return "minus " + numberToWords(-num);
if (num < 10) return units[num];
if (num < 20) return teens[num - 10];

if (num < 100) {
int tenPart = num / 10;
int unitPart = num % 10;
return (unitPart == 0)
? tens[tenPart]
: tens[tenPart] + " " + units[unitPart];
}

if (num < 1000) {
int hundredPart = num / 100;
int remainder = num % 100;
return (remainder == 0)
? units[hundredPart] + " hundred"
: units[hundredPart] + " hundred " + numberToWords(remainder);
}

if (num < 10000) {
int thousandPart = num / 1000;
int remainder = num % 1000;
return (remainder == 0)
? units[thousandPart] + " thousand"
: units[thousandPart] + " thousand " + numberToWords(remainder);
}

return "Number too large";
}

// 10. Length of the longest substring without repeating characters
public static int longestUniqueSubstring(String s) {
int n = s.length();
int maxLength = 0;

int[] lastIndex = new int[256];
for (int i = 0; i < 256; i++) {
lastIndex[i] = -1;
}

int start = 0;

for (int end = 0; end < n; end++) {
char current = s.charAt(end);

if (lastIndex[current] >= start) {
start = lastIndex[current] + 1;
}

lastIndex[current] = end;
maxLength = Math.max(maxLength, end - start + 1);
}

return maxLength;
}
}