Other.java

package Stack;

public class Other {

    static String lexicoMaxSubsequence(String s, int n)
    {
        Stack<Character> st = new Stack<Character>();
 
        // Stores if any alphabet is present
        // in the current stack
        int[] visited = new int[26];
        int[] cnt = new int[26];
        for (int i = 0; i < 26; i++) {
            visited[i] = 0;
            cnt[i] = 0;
        }
 
        // Findthe number of occurrences of
        // the character s[i]
        for (int i = 0; i < n; i++) {
            cnt[s.charAt(i) - 'a']++;
        }
        for (int i = 0; i < n; i++) {
 
            // Decrease the character count
            // in remaining string
            cnt[s.charAt(i) - 'a']--;
 
            // If character is already present
            // in the stack
            if (visited[s.charAt(i) - 'a'] > 0) {
                continue;
            }
 
            // if current character is greater
            // than last character in stack
            // then pop the top character
            while (!st.empty() && st.peek() < s.charAt(i)
                   && cnt[st.peek() - 'a'] != 0) {
                visited[st.peek() - 'a'] = 0;
                st.pop();
            }
 
            // Push the current character
            st.push(s.charAt(i));
            visited[s.charAt(i) - 'a'] = 1;
        }
 
        // Stores the resultant string
        String s1 = "";
 
        // Generate the string
        while (!st.empty()) {
            s1 = st.peek() + s1;
            st.pop();
        }
 
        // Return the resultant string
        return s1;
    }
    public static void main(String[] args) {
        String S = "ababc";
        int N = S.length();
        System.out.println(lexicoMaxSubsequence(S, N));
    }
}