Remove Duplicate Numbers in Array(lintcode 521)

Description

Given an array of integers, remove the duplicate numbers in it.

You should:

1. Do it in place in the array.
2. Move the unique numbers to the front of the array.
3. Return the total number of the unique numbers.

Notice:
You don't need to keep the original order of the integers.

Example

Given nums = [1,3,1,4,4,2], you should:

Move duplicate integers to the tail of nums => nums = [1,3,4,2,?,?]. Return the number of unique integers in nums => 4. Actually we don't care about what you place in ?, we only care about the part which has no duplicate integers.

Interface

public class Solution {
    /**
     * @param nums an array of integers
     * @return the number of unique integers
     */
    public int deduplication(int[] nums) {
        // Write your code here
    }
}

Idea

Use the HashSet to get unique numbers.

Solution

public class Solution {
    /**
     * @param nums an array of integers
     * @return the number of unique integers
     */
    public int deduplication(int[] nums) {
        // Write your code here
        HashSet<Integer> uniqueNums = new HashSet<Integer>();
        for (int i = 0; i < nums.length; ++i) {
            uniqueNums.add(nums[i]);
        }
        int i = 0;
        for (Integer num : uniqueNums) {
            nums[i] = num;
            ++i;
        }
        return uniqueNums.size();
    }
}