LeetCode 1447. 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. You can return the answer 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".

Constraints:

• 1 <= n <= 100

判断每个可能的分数，那么就要挨个去遍历，但是考虑到1/2跟2/4是一样的，所以就要求最大公约数，GCD，我又卡在这里了，还好不难，剩下的就是避免重复，要用hashset去依次判断，然后返回即可；

下面是代码：

Hide Hint 1

A fraction is fully simplified if there is no integer that divides cleanly into the numerator and denominator.

Hide Hint 2

In other words the greatest common divisor of the numerator and the denominator of a simplified fraction is 1.

Problems

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Runtime: 44 ms, faster than 19.02% of Java online submissions for Simplified Fractions.

Memory Usage: 45.2 MB, less than 6.75% of Java online submissions for Simplified Fractions.