Problem: 2050E - Three Strings
Language: java

Solution 1 (runtime: 234 ms):
import java.util.Scanner;
public class Main{
	private static int solve(String a, String b, String c, int ai, int bi, int ci, int[][] dp) {
		if (ai==a.length()) {
			int diff = 0;
			for(int i=bi;i<b.length();i++) {
				diff += (b.charAt(i)==c.charAt(ci++)?0:1);
			}
			return diff;
		}
		if (bi==b.length()) {
			int diff = 0;
			for(int i=ai;i<a.length();i++) {
				diff += (a.charAt(i)==c.charAt(ci++)?0:1);
			}
			return diff;
		}
		if (dp[ai][bi]!=-1) {
			return dp[ai][bi];
		}
		// take from a
		int takeFromA = solve(a, b, c, ai+1, bi, ci+1,dp) + (a.charAt(ai)==c.charAt(ci)?0:1);
		int takeFromB = solve(a, b, c, ai, bi+1, ci+1,dp) + (b.charAt(bi)==c.charAt(ci)?0:1);
		return dp[ai][bi] = Math.min(takeFromA, takeFromB);
	}
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int t = sc.nextInt();
		while (t-->0) {
			String a,b,c;
			a = sc.next();
			b = sc.next();
			c = sc.next();
			int dp[][] = new int[a.length()][b.length()];
			for (int i=0;i<dp.length;i++) {
				for(int j=0;j<dp[i].length;j++) {
					dp[i][j] = -1;
				}
			}
			System.out.println(solve(a,b,c,0,0,0,dp));
		}
	}
}

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();
    }
}