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: 390 ms):
import java.util.*;

public class Q1 {
    public static long solve(long n, HashMap<Long, Long> map) {
        if (n <= 3) {
            return 1;
        }

        if (map.containsKey(n)) {
            return map.get(n);
        }

        long count = solve(n / 4, map) + solve(n / 4, map);
        map.put(n, count);
        return map.get(n);
    }

    public static long gcd(long a, long b) {
        if (a == 0)
            return b;
        if (b == 0)
            return a;

        // Base case
        if (a == b)
            return a;

        // a is greater
        if (a > b) {
            if (a % b == 0)
                return b;
            return gcd(a - b, b);
        }
        if (b % a == 0)
            return a;
        return gcd(a, b - a);
    }

    public static int solve(int ai, int ci, String a, String b, String c, int dp[][]) {
        int bi = ci - ai;
        if (ai == a.length()) {
            String s1 = b.substring(bi);
            String s2 = c.substring(ci);
            if (s1.equals(s2)) {
                return 0;
            }
            int cnt = 0;
            for (int i = 0; i < s1.length(); i++) {
                if (s1.charAt(i) != s2.charAt(i)) {
                    cnt++;
                }
            }

            return cnt;
        }

        if (bi == b.length()) {
            String s1 = a.substring(ai);
            String s2 = c.substring(ci);
            if (s1.equals(s2)) {
                return 0;
            }
            int cnt = 0;
            for (int i = 0; i < s1.length(); i++) {
                if (s1.charAt(i) != s2.charAt(i)) {
                    cnt++;
                }
            }

            return cnt;
        }

        if (dp[ai][ci] != -1) {
            return dp[ai][ci];
        }

        int min = Integer.MAX_VALUE;
        if (a.charAt(ai) == c.charAt(ci)) {
            min = Math.min(solve(ai + 1, ci + 1, a, b, c, dp), min);
        }

        if (b.charAt(bi) == c.charAt(ci)) {
            min = Math.min(solve(ai, ci + 1, a, b, c, dp), min);
        }

        if (a.charAt(ai) != c.charAt(ci) || b.charAt(bi) != c.charAt(ci)) {
            min = Math.min(1 + Math.min(solve(ai + 1, ci + 1, a, b, c, dp), solve(ai, ci + 1, a, b, c, dp)), min);
        }

        return dp[ai][ci] = min;
    }

    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 dp[][] = new int[a.length()][c.length()];
            for (int row[] : dp) {
                Arrays.fill(row, -1);
            }
            System.out.println(solve(0, 0, a, b, c, dp));
        }
    }
}