N-Repeated Element in Size 2N Array Problem & Solution

You are given an integer array nums with the following properties:

  • nums.length == 2 * n.
  • nums contains n + 1 unique elements.
  • Exactly one element of nums is repeated n times.

Return the element that is repeated n times.

See the n-repeated element in size 2n array problem on LeetCode.

C++ Solution

#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")
#pragma GCC target("avx,avx2,fma")

static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

class Solution {
public:
  int repeatedNTimes(vector<int>& nums) {
    for (int i = 2; i < nums.size(); ++i) {
      if (nums[i - 2] == nums[i] || nums[i - 1] == nums[i]) {
        return nums[i];
      }
    }

    return nums[0];
  }
};

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