Submission #94341

#	Time	Username	Problem	Language	Result	Execution time	Memory
94341		zeyad49	Savez (COCI15_savez)	Java	120 / 120	530 ms	51812 KiB

savez

/*
 *  for each string, let dp[i] = the maximum length of a subsequence ending at i, for a string s 
 *  we know that s will extend on a prefix of s, so let us search for all prefixes of s, and if the prefix matches the suffix
 *  we say that we can extend i to the dp of the prefix, and we implement this efficiently using hashing
 */
import java.io.*;
import java.util.*;

class savez {

	static int n;

	static int MOD = (int) 1e9 + 9, p = 31, maxN = (int) 2e6 + 5;;

	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner();
		PrintWriter out = new PrintWriter(System.out);

		n = sc.nextInt();
		int ans = 1;
		HashMap<Integer, Integer> map = new HashMap();
		for (int i = 0; i < n; i++) {
			char[] s = sc.next().toCharArray();
			int len = s.length;
			int[] hash = new int[len];
			long pow = 1;
			long last = 0;
			for (int j = 0; j < len; j++) {
				last = last + (s[j] - 'A' + 1) * 1l * pow;
				last %= MOD;
				hash[j] = (int) last;
				pow = pow * p % MOD;
			}

			int dp = 1;
			pow = 1;
			for (int prefix = len; prefix > 0; prefix--) {
				int preHash = hash[prefix - 1], sufHash = hash[len - 1] - (prefix == len ? 0 : hash[len - 1 - prefix]);
				if (sufHash < 0)
					sufHash += MOD;
				if (sufHash == (preHash * 1l * pow % MOD))
					dp = Math.max(dp, 1 + map.getOrDefault(preHash, 0));
				pow = pow * p % MOD;
			}
			map.put(hash[len - 1], dp);
			ans = Math.max(ans, dp);
		}
		out.println(ans);

		out.close();

	}

	static class Scanner {
		BufferedReader br;
		StringTokenizer st;

		Scanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		Scanner(String fileName) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(fileName));
		}

		String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

		String nextLine() throws IOException {
			return br.readLine();
		}

		int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		long nextLong() throws NumberFormatException, IOException {
			return Long.parseLong(next());
		}

		double nextDouble() throws NumberFormatException, IOException {
			return Double.parseDouble(next());
		}
	}
}

Compilation message (stderr)

Note: savez.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

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