0448. Find All Numbers Disappeared in an Array
https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array
Description
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
.
Example 1:
**Input:** nums = [4,3,2,7,8,2,3,1]
**Output:** [5,6]
Example 2:
**Input:** nums = [1,1]
**Output:** [2]
Constraints:
n == nums.length
1 <= n <= 105
1 <= nums[i] <= n
Follow up: Could you do it without extra space and in O(n)
runtime? You may assume the returned list does not count as extra space.
ac
class Solution {
public List<Integer> findDisappearedNumbers(int[] nums) {
List<Integer> res = new ArrayList<Integer>();
// corner cases
if (nums.length == 0) return res;
// iterate
int n = nums.length;
for (int i = 0; i < n; i++) {
while (nums[i] < n && i != nums[i] && nums[nums[i]] != nums[i]) {
swap(nums, i, nums[i]);
}
// special case, n
if (nums[i] == n) swap(nums, 0, i);
}
// final check get result
if (nums[0] != n) res.add(n);
for (int i = 1; i < n; i++) {
if (nums[i] != i) {
res.add(i);
}
}
return res;
}
private void swap(int[] nums, int i, int j) {
int tmp = nums[i];
nums[i] = nums[j];
nums[j] = tmp;
}
}
/*
make use of index, make nums[i] = i, careful: if nums[i] == n, swap to nums[0]
*/
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