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solution.java
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solution.java
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//String algorithms--> Two Characters
import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;
public class solution {
static int alternate(String s) {
if(s.length()<=1) //base case
return 0;
int[][] pair = new int[26][26]; //choice of pairs of laternating characters
int[][] count = new int[26][26]; //keeps track of the length possible for each pair of choice
for (int i = 0; i < s.length(); i++) {
char letter = s.charAt(i);
int letterNum = letter - 'a';
// Updating the row corresponding to the current character
for (int col = 0; col < 26; col++) {
if (pair[letterNum][col] == letter) {
count[letterNum][col] = -1;
}
if (count[letterNum][col] != -1) {
pair[letterNum][col] = letter;
count[letterNum][col]++;
}
}
// Updating column corresponding to the current character
for (int row = 0; row < 26; row++) {
if (pair[row][letterNum] == letter) {
count[row][letterNum] = -1;
}
if (count[row][letterNum] != -1) {
pair[row][letterNum] = letter;
count[row][letterNum]++;
}
}
}
//Finding maxlen from "count" array
int maxlen = 0;
for (int row = 0; row < 26; row++) {
for (int col = 0; col < 26; col++) {
maxlen = Math.max(maxlen, count[row][col]);
}
}
return maxlen;
}
public static void main(String[] args) throws IOException {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
int l = Integer.parseInt(bufferedReader.readLine().trim());
String s = bufferedReader.readLine();
int result = alternate(s);
bufferedWriter.write(String.valueOf(result));
bufferedWriter.newLine();
bufferedReader.close();
bufferedWriter.close();
}
}