Simplified Fractions

Given an integer n, return a list of all simplified fractions between 0 and 1 (exclusive) such that the denominator is less-than-or-equal-to n. The fractions can be in any order.

Example 1:

Input: n = 2
Output: ["1/2"]
Explanation: "1/2" is the only unique fraction with a denominator less-than-or-equal-to 2.

Example 2:

Input: n = 3
Output: ["1/2","1/3","2/3"]

Example 3:

Input: n = 4
Output: ["1/2","1/3","1/4","2/3","3/4"]
Explanation: "2/4" is not a simplified fraction because it can be simplified to "1/2".

Example 4:

Input: n = 1
Output: []

Constraints:

• 1 <= n <= 100

class Solution {
    private int gcd(int x, int y) {
        if (y == 0)
            return x;
        return gcd(y, x % y);
    }

    public List<String> simplifiedFractions(int n) {
        List<String> ans = new ArrayList<>();
        Set<String> set = new HashSet<>();
        for (int i = 2; i <= n; i++) {
            for (int j = 1; j < i; j++) {
                int gcd = gcd(i, j);
                int num = j / gcd, deno = i / gcd;
                StringBuilder str = new StringBuilder();
                str.append(Integer.toString(num) + "/" + Integer.toString(deno));
                if (!set.contains(str.toString())) {
                    set.add(str.toString());
                    ans.add(str.toString());
                }
            }
        }
        return ans;
    }
}