Problem: 2050E - Three Strings
Language: java

Solution 1 (runtime: 343 ms):
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int t=sc.nextInt();
        while (t-->0){
           String a=sc.next();
           String b=sc.next();
           String c=sc.next();
           int[][] f=new int[a.length()+1][b.length()+1];
            for (int i = 0; i < a.length(); i++) {
                f[i+1][0]=f[i][0]+(a.charAt(i)==c.charAt(i)?0:1);
            }
            for (int i = 0; i < b.length(); i++) {
                f[0][i+1]=f[0][i]+(b.charAt(i)==c.charAt(i)?0:1);
            }
            f[0][0]=0;
            for (int i = 1; i <= a.length(); i++) {
                for (int j = 1; j <= b.length(); j++) {
                    f[i][j]=Integer.MAX_VALUE;
                    f[i][j]=Math.min(f[i][j],f[i-1][j]+(a.charAt(i-1)==c.charAt(i+j-1)? 0 : 1));
                    f[i][j]=Math.min(f[i][j],f[i][j-1]+(b.charAt(j-1)==c.charAt(i+j-1)? 0 : 1));
                }
            }
            System.out.println(f[a.length()][b.length()]);
        }
    }
}

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();
    }
}