ExtractUniqueCharacters.java

// Extract Unique characters
// Send Feedback
// Given a string S, you need to remove all the duplicates. That means, the
// output string should contain each character only once. The respective order
// of characters should remain same, as in the input string.
// Input format:
// The first and only line of input contains a string, that denotes the value of
// S.
// Output format :
// The first and only line of output contains the updated string, as described
// in the task.
// Constraints :
// 0 <= Length of S <= 10^8
// Time Limit: 1 sec
// Sample Input 1 :
// ababacd
// Sample Output 1 :
// abcd
// Sample Input 2 :
// abcde
// Sample Output 2 :
// abcde

import java.util.HashMap;

public class Solution {

    public static String uniqueChar(String str) {
        /*
         * Your class should be named Solution
         * Don't write main().
         * Don't read input, it is passed as function argument.
         * Return output and don't print it.
         * Taking input and printing output is handled automatically.
         */
        HashMap<Character, Integer> map = new HashMap<>();
        String ans = "";
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (map.containsKey(ch)) {
                map.put(ch, map.get(ch) + 1);
            } else {
                map.put(ch, 1);
                ans += ch;
            }
        }

        return ans;

    }
}