Submission #71329018

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Source Code Expand

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        FastScanner in = new FastScanner();
        PrintWriter out = new PrintWriter(System.out);

        try {
            String tLine = in.next();
            if (tLine == null) return;
            int T = Integer.parseInt(tLine);

            while (T-- > 0) {
                String nLine = in.next();
                if (nLine == null) break;
                int N = Integer.parseInt(nLine);
                
                String[] s = new String[N];
                for (int i = 0; i < N; i++) {
                    s[i] = in.next();
                }

                
                Arrays.sort(s, (s1, s2) -> {
                    int len1 = s1.length();
                    int len2 = s2.length();
                    int total = len1 + len2;
                    for (int k = 0; k < total; k++) {
                        char c1 = (k < len1) ? s1.charAt(k) : s2.charAt(k - len1);
                        char c2 = (k < len2) ? s2.charAt(k) : s1.charAt(k - len2);
                        if (c1 != c2) return c1 - c2;
                    }
                    return 0;
                });

                
                boolean duplicateFound = false;
                for (int i = 0; i < N - 1; i++) {
                    if (isCommutative(s[i], s[i+1])) {
                        duplicateFound = true;
                        break;
                    }
                }

                
                if (!duplicateFound) {
                    String temp = s[N - 1];
                    s[N - 1] = s[N - 2];
                    s[N - 2] = temp;
                }

                StringBuilder sb = new StringBuilder();
                for (String str : s) sb.append(str);
                out.println(sb);
            }
        } catch (Exception e) {
        }
        
        out.flush();
    }

    // Optimized helper to check s1 + s2 == s2 + s1 without creating new Strings
    private static boolean isCommutative(String s1, String s2) {
        int l1 = s1.length();
        int l2 = s2.length();
        int total = l1 + l2;
        for (int k = 0; k < total; k++) {
            char c1 = (k < l1) ? s1.charAt(k) : s2.charAt(k - l1);
            char c2 = (k < l2) ? s2.charAt(k) : s1.charAt(k - l2);
            if (c1 != c2) return false;
        }
        return true;
    }

    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        String next() {
            while (!st.hasMoreTokens()) {
                try {
                    String line = br.readLine();
                    if (line == null) return null;
                    st = new StringTokenizer(line);
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }
    }
}

Submission Info

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