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# Posts published in “Randomization”

In a array A of size 2N, there are N+1 unique elements, and exactly one of these elements is repeated N times.

Return the element repeated N times.

Example 1:

Input: [1,2,3,3]Output: 3

Example 2:

Input: [2,1,2,5,3,2]Output: 2

Example 3:

Input: [5,1,5,2,5,3,5,4]Output: 5

Note:

1. 4 <= A.length <= 10000
2. 0 <= A[i] < 10000
3. A.length is even

# Solution: Randomization

Randomly pick two numbers in the array, if they are the same (25% probability) return the number, do it until the two numbers are the same.

Time complexity: O(1) expected 4
Space complexity: O(1)