First Missing Positive
Given an unsorted integer array nums
. Return the smallest positive integer that is not present in nums
.
You must implement an algorithm that runs in O(n)
time and uses O(1)
auxiliary space.
Example 1:
Input: nums = [1,2,0]
Output: 3
Explanation: The numbers in the range [1,2] are all in the array.
Example 2:
Input: nums = [3,4,-1,1]
Output: 2
Explanation: 1 is in the array but 2 is missing.
Example 3:
Input: nums = [7,8,9,11,12]
Output: 1
Explanation: The smallest positive integer 1 is missing.
public class Solution
{
public int solution(int[] nums)
{
if (nums?.Length > 0)
{
HashSet<int> set = new(nums);
int i = 1;
while (set.Contains(i))
{
i++;
}
return i;
}
return 0;
}
}
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