Problem: 2050E - Three Strings
Language: java

Solution 1 (runtime: 233 ms):
import java.util.Scanner;

public class Main {
    private static final int MAX_LEN = 2003; // Ensure larger array size for safety

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int t = scanner.nextInt();
        scanner.nextLine(); // Consume the newline character

        while (t-- > 0) {
            String a = scanner.nextLine();
            String b = scanner.nextLine();
            String c = scanner.nextLine();

            int n = a.length();
            int m = b.length();
            int[][] dp = new int[n + 1][m + 1]; // Use n + 1 and m + 1 for proper indexing

            for (int i = 0; i <= n; i++) {
                for (int j = 0; j <= m; j++) {
                    dp[i][j] = MAX_LEN; // Initialize with a large value
                }
            }

            dp[0][0] = 0;

            for (int i = 0; i <= n; i++) {
                for (int j = 0; j <= m; j++) {
                    if (i > 0) {
                        dp[i][j] = Math.min(dp[i][j], dp[i - 1][j] + (a.charAt(i - 1) != c.charAt(i + j - 1) ? 1 : 0));
                    }
                    if (j > 0) {
                        dp[i][j] = Math.min(dp[i][j], dp[i][j - 1] + (b.charAt(j - 1) != c.charAt(i + j - 1) ? 1 : 0));
                    }
                }
            }

            System.out.println(dp[n][m]);
        }
        scanner.close(); // Close the scanner to avoid resource leaks
    }
}


Solution 2 (runtime: 280 ms):
import java.util.*;

public class ThreeStrings {
    // Custom print functions
    public static void print(Object print) {
        System.out.print(print);
    }

    public static void println(Object print) {
        System.out.println(print);
    }

    public static void println() {
        System.out.println();
    }

    // Declare a 2D dp array to store memoization results
    static int[][] dp;

    // Function to compute the minimum changes required
    public static int func(int i, int j, char[] a, char[] b, char[] c) {
        int n = c.length;
        // Base case: if all characters are matched
        if (i + j >= n) return 0;

        // Check if result is already calculated
        if (dp[i][j] != -1) return dp[i][j];

        int take_a = Integer.MAX_VALUE;
        int take_b = Integer.MAX_VALUE;

        // Try taking a character from 'a'
        if (i < a.length) {
            if (a[i] == c[i + j]) {
                take_a = func(i + 1, j, a, b, c); // No change needed
            } else {
                take_a = 1 + func(i + 1, j, a, b, c); // Change needed
            }
        }

        // Try taking a character from 'b'
        if (j < b.length) {
            if (b[j] == c[i + j]) {
                take_b = func(i, j + 1, a, b, c); // No change needed
            } else {
                take_b = 1 + func(i, j + 1, a, b, c); // Change needed
            }
        }

        // Store and return the minimum changes required
        return dp[i][j] = Math.min(take_a, take_b);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt(); // Number of test cases

        for (int l = 0; l < t; l++) {
            char[] a = sc.next().toCharArray(); // Input string a
            char[] b = sc.next().toCharArray(); // Input string b
            char[] c = sc.next().toCharArray(); // Target string c

            int m = a.length;
            int n = b.length;
            int len = c.length;

            // Initialize dp array with -1
            dp = new int[m + 1][n + 1];
            for (int[] row : dp) {
                Arrays.fill(row, -1);
            }

            // Compute and print result
            println(func(0, 0, a, b, c));
        }
        sc.close();
    }
}