Missing Number LeetCode solution in Java

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// Approach 1: Find diff
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class Solution {
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  public int missingNumber(int[] nums) {
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    int n = nums.length;
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    int expectedSum = (n * (n + 1)) / 2;
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    for (int num : nums) expectedSum -= num;
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    return expectedSum;
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  }
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}
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// Approach 2: XOR
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class Solution {
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  public int missingNumber(int[] nums) {
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    int xor1 = 0;
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    for (int i = 1; i <= nums.length; i++) xor1 = xor1 ^ i;
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    int xor2 = 0;
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    for (int num : nums) xor2 = xor2 ^ num;
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    return xor1 ^ xor2;
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  }
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}
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// Approach 3: Cyclic sort
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class Solution {
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  public int missingNumber(int[] nums) {
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    int i = 0;
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    while (i < nums.length) {
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      if (nums[i] != i && nums[i] < nums.length) swap(i, nums[i], nums);
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      else i += 1;
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    }
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    for (int j = 0; j < nums.length; j++) {
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      if (nums[j] != j) return j;
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    }
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    return nums.length;
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  }
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  private void swap(int i, int j, int[] nums) {
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    int temp = nums[i];
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    nums[i] = nums[j];
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    nums[j] = temp;
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  }
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}