Rambabu Kola

----------------- SDET Coding Questions ------------------

Java & Data Structures
1. Reverse a string without using reverse() public class ReverseString {
public static void main(String[] args) {
String input = "hello"; String reversed = ""; for (int i = input.length() - 1; i >= 0; i--) { reversed += input.charAt(i);
}
System.out.println("Reversed: " + reversed);
}
}

2. Check if a string is a palindrome
public class PalindromeCheck { public static void main(String[] args) {
String input = "madam";
String reversed = new StringBuilder(input).reverse().toString();
System.out.println("Is palindrome: " + input.equals(reversed));
}
}

3. Find the first non-repeating character in a string import java.util.*; public class FirstNonRepeatingChar { public static void main(String[] args) {
String input = "aabbcdeff";
Map<Character, Integer> map = new LinkedHashMap<>(); for (char c : input.toCharArray()) { map.put(c, map.getOrDefault(c, 0) + 1);
}
for (char c : map.keySet()) { if (map.get(c) == 1) {
System.out.println("First non-repeating: " + c); break;
}
}
}
}

4. Count frequency of each character in a string import java.util.*; public class CharFrequency { public static void main(String[] args) {
String input = "aabbccdde";
Map<Character, Integer> freq = new HashMap<>(); for (char c : input.toCharArray()) { freq.put(c, freq.getOrDefault(c, 0) + 1);
}
System.out.println(freq);
}
}

5. Remove duplicate characters from a string
public class RemoveDuplicatesFromString { public static void main(String[] args) {
String input = "aabbccde";
StringBuilder result = new StringBuilder(); Set<Character> seen = new HashSet<>(); for (char c : input.toCharArray()) { if (!seen.contains(c)) { seen.add(c); result.append(c);
} } System.out.println("Without duplicates: " + result.toString());
}
}

6. Check if two strings are anagrams import java.util.*; public class AnagramCheck {
public static void main(String[] args) {
String s1 = "listen";
String s2 = "silent"; char[] arr1 = s1.toCharArray(); char[] arr2 = s2.toCharArray();
Arrays.sort(arr1);
Arrays.sort(arr2);
System.out.println("Are anagrams: " + Arrays.equals(arr1, arr2));
}
}

7. Sort an array using bubble sort import java.util.*; public class BubbleSort { public static void main(String[] args) { int[] arr = {5, 2, 9, 1}; for (int i = 0; i < arr.length - 1; i++) { for (int j = 0; j < arr.length - 1 - i; j++) { if (arr[j] > arr[j + 1]) { int temp = arr[j]; arr[j] = arr[j + 1]; arr[j + 1] = temp;
}
}
}
System.out.println(Arrays.toString(arr));
}
}

8. Sort an array using selection sort import java.util.*; public class SelectionSort { public static void main(String[] args) { int[] arr = {5, 2, 9, 1}; for (int i = 0; i < arr.length - 1; i++) { int minIndex = i; for (int j = i + 1; j < arr.length; j++) { if (arr[j] < arr[minIndex]) { minIndex = j;
}
}
int temp = arr[minIndex]; arr[minIndex] = arr[i]; arr[i] = temp;
}
System.out.println(Arrays.toString(arr));
}
}

9. Find the second largest number in an array public class SecondLargest { public static void main(String[] args) { int[] arr = {10, 20, 4, 45, 99}; int first = Integer.MIN_VALUE; int second = Integer.MIN_VALUE; for (int num : arr) { if (num > first) { second = first; first = num;
} else if (num > second && num != first) {
second = num;
}
}
System.out.println("Second largest: " + second);
}
}

10. Find the missing number from an array of 1 to n public class MissingNumber { public static void main(String[] args) { int[] arr = {1, 2, 4, 5, 6}; int n = 6; int sum = n * (n + 1) / 2; for (int num : arr) { sum -= num;
}
System.out.println("Missing number: " + sum);
}
}

4 months ago | [YT] | 0