# Find All Numbers Disappeared in an Array

Given an array nums of n integers where nums[i] is in the range [1, n], return *an array of all the integers in the range* [1, n] *that do not appear in* nums.

```
class Solution {
public List<Integer> findDisappearedNumbers(int[] nums) {
Set<Integer> set = new HashSet<>();
for (int val : nums) {
set.add(val);
}
ArrayList<Integer> list = new ArrayList<>();
for (int i = 1; i <= nums.length; i++) {
if (!set.contains(i)) {
list.add(i);
}
}
return list;
}
}
```

## Related Problems

Given an array of **distinct** integers candidates and a target integer target, return *a list of all ***unique combinations*** of *candidates* where the chosen numbers sum to *target*.* You may return the combinations in **any order**.

The **same** number may be chosen from candidates an **unlimited number of times**. Two combinations are unique if the frequency of at least one of the chosen numbers is different.

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, bi] indicates that you **must** take course bi first if you want to take course ai.

For example, the pair [0, 1], indicates that to take course 0 you have to first take course 1.

Return true if you can finish all courses. Otherwise, return false.

Given a string s and an integer k, return the length of the longest substring of s that contains at most k distinct characters.

Given the head of a linked list, return *the list after sorting it in ***ascending order**.