哈希集合、间隔、随机化：3 种方法求解《961. 在长度 2N 的数组中找出重复 N 次的元素》

var repeatedNTimes = function(nums) {
  const h = new Uint8Array(10 ** 4 + 1)
  for (let i = 0; i < nums.length; i++) {
    if (h[nums[i]] === 1) return nums[i]
    h[nums[i]] = 1
  }
};

var repeatedNTimes = function(nums) {
  const h = new Set
  for (let i = 0; i < nums.length; i++) {
    if (h.has(nums[i])) return nums[i]
    h.add(nums[i])
  }
};

var repeatedNTimes = function(nums) {
  const h = Object.create(null)
  for (let i = 0; i < nums.length; i++) {
    if (h[nums[i]] !== void 0) return nums[i]
    h[nums[i]] = 1
  }
};

function repeatedNTimes(nums: number[]): number {
  const s = new Set
  for (let i = 0; i < nums.length; i++) {
    if (s.has(nums[i])) return nums[i]
    s.add(nums[i])
  }
};

func repeatedNTimes(nums []int) int {
  type void struct{}
  var value void
  s := make(map[int]void)
  for _, num := range nums {
    if _, ok := s[num]; ok {
      return num
    }
    s[num] = value
  } 
  return -1
}

func repeatedNTimes(nums []int) int {
  s := map[int]bool{}
  for _, num := range nums {
    if s[num] {
      return num
    }
    s[num] = true
  } 
  return -1
}

class Solution {
  function repeatedNTimes($nums) {
    $s = [];
    foreach ($nums as $num) {
      if ($s[$num]) return $num;
      $s[$num] = 1;
    }
  }
}

class Solution:
  def repeatedNTimes(self, nums: List[int]) -> int:
    s = set()
    for num in nums:
      if num in s:
        return num
      s.add(num)

class Solution {
  public int repeatedNTimes(int[] nums) {
    Set<Integer> s = new HashSet<Integer>();
    for (int num : nums) {
      if (s.contains(num)) return num;
      s.add(num);
    }
    return -1;
  }
}

var repeatedNTimes = function(nums) {
  const n = nums.length
  for (let gap = 1; gap <= 3; gap++) {
    for (let i = 0; i + gap < n; i++) {
      if (nums[i] === nums[i + gap]) return nums[i]
    }
  }
};

function repeatedNTimes(nums: number[]): number {
  const n = nums.length
  for (let gap = 1; gap <= 3; gap++) {
    for (let i = 0; i + gap < n; i++) {
      if (nums[i] === nums[i + gap]) return nums[i]
    }
  }
};

func repeatedNTimes(nums []int) int {
  n := len(nums)
  for gap := 1; gap <= 3; gap++ {
    for i := 0; i + gap < n; i++ {
      if nums[i] == nums[i + gap] {
        return nums[i]
      }
    }
  }
  return -1
}

class Solution {
  function repeatedNTimes($nums) {
    $n = count($nums);
    for ($gap = 1; $gap <= 3; $gap++) {
      for ($i = 0; $i + $gap < $n; $i++) {
        if ($nums[$i] === $nums[$i + $gap]) return $nums[$i];
      }
    }
  }
}

class Solution:
  def repeatedNTimes(self, nums: List[int]) -> int:
    n = len(nums)
    for gap in range(1, 4):
      for i in range(0, n -gap):
        if nums[i] == nums[i + gap]: return nums[i]

class Solution {
  public int repeatedNTimes(int[] nums) {
    int n = nums.length;
    for (int gap = 1; gap <= 3; gap++) {
      for (int i = 0; i + gap < n; i++) {
        if (nums[i] == nums[i + gap]) return nums[i];
      }
    }
    return -1;
  }
}

var repeatedNTimes = function(nums) {
  const n = nums.length
  while (true) {
    const x = Math.random() * n | 0, y = Math.random() * n | 0
    if (x !== y && nums[x] === nums[y]) return nums[x]
  }
};

function repeatedNTimes(nums: number[]): number {
  const n = nums.length
  while(true) {
    const x = Math.random() * n >> 0, y = Math.random() * n >> 0
    if (x !== y && nums[x] === nums[y]) return nums[x]
  }
};

function repeatedNTimes(nums: number[]): number {
  const n = nums.length
  while(true) {
    const x = ~~(Math.random() * n), y = ~~(Math.random() * n)
    if (x !== y && nums[x] === nums[y]) return nums[x]
  }
};

func repeatedNTimes(nums []int) int {
  n := len(nums)
  for {
    x, y := rand.Intn(n), rand.Intn(n)
    if x != y && nums[x] == nums[y] {
      return nums[x]
    }
  }
}

class Solution {
  function repeatedNTimes($nums) {
    $n = count($nums);
    while (true) {
      $x = rand(0, $n);
      $y = rand(0, $n);
      if ($x !== $y && $nums[$x] === $nums[$y]) return $nums[$x];
    }
  }
}

class Solution:
  def repeatedNTimes(self, nums: List[int]) -> int:
    n = len(nums)
    while True:
      x, y = random.randrange(n), random.randrange(n)
      if x != y and nums[x] == nums[y]: return nums[x]

class Solution {
  public int repeatedNTimes(int[] nums) {
    int n = nums.length;
    Random random = new Random();
    while (true) {
      int x = random.nextInt(n);
      int y = random.nextInt(n);
      if (x != y && nums[x] == nums[y]) return nums[x];
    }
  }
}