A. Festival Greeting

A simple greetign problem to start the contest.

public class Greeting {
    public static void main(String[] args) {
        System.out.println("Happy Lantern Festival!");
    }
}

B. Lantern Riddles

Simulate solving lantern riddles in a circular arrangement.

import java.util.*;

public class RiddleSolver {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int size = input.nextInt();
        int[] nums = new int[size];
        for (int i = 0; i < size; i++) {
            nums[i] = input.nextInt();
        }
        
        List<Integer> results = new ArrayList<>();
        for (int i = 0; i < size; i++) {
            int left = (i - 1 + size) % size;
            int right = (i + 1) % size;
            results.add(nums[left] + nums[right]);
        }
        System.out.println(String.join(" ", 
            results.stream().map(String::valueOf).toArray(String[]::new)));
    }
}

C. Math Genius

Calculate the sum of absolute values of array elements.

import java.util.Scanner;

public class AbsoluteSum {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int count = sc.nextInt();
        long total = 0;
        
        for (int i = 0; i < count; i++) {
            total += Math.abs(sc.nextLong());
        }
        System.out.println(total);
    }
}

D. Equation Solver

Solve a specific quadratic equation problem.

import java.util.Scanner;

public class EquationChecker {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int cases = input.nextInt();
        
        while (cases-- > 0) {
            long value = input.nextLong();
            if (value % 4 != 0) {
                System.out.println("No");
            } else {
                long solution = value / 4 - 1;
                if (solution <= 0 || solution % 2 == 0) {
                    System.out.println("No");
                } else {
                    System.out.println("Yes");
                    System.out.println(solution + " " + (solution + 2));
                }
            }
        }
    }
}

E. Isosceles Triangle

Find maximum number of valid isosceles triangle pairs.

import java.util.Arrays;
import java.util.Scanner;

public class TriangleFinder {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] sides = new int[n];
        int[] bases = new int[n];
        
        for (int i = 0; i < n; i++) sides[i] = sc.nextInt();
        for (int i = 0; i < n; i++) bases[i] = sc.nextInt();
        
        Arrays.sort(sides);
        Arrays.sort(bases);
        
        int count = 0, index = 0;
        for (int base : bases) {
            while (index < n && sides[index] * 2 <= base) {
                index++;
            }
            if (index < n) {
                index++;
                count++;
            }
        }
        System.out.println(count);
    }
}

F. Equation Calculation

Use binary seearch to solve a logarithmic equation.

import java.util.Scanner;

public class EquationBinarySearch {
    static boolean isValid(int x, int k, int m) {
        double root = Math.sqrt(x);
        double log = Math.log(x) / Math.log(k);
        return root + log > m;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int tests = sc.nextInt();
        
        while (tests-- > 0) {
            int k = sc.nextInt(), m = sc.nextInt();
            int left = 1, right = m * m;
            while (left <= right) {
                int mid = left + (right - left) / 2;
                if (isValid(mid, k, m)) {
                    right = mid - 1;
                } else {
                    left = mid + 1;
                }
            }
            System.out.println(left);
        }
    }
}