Missing Number (https://leetcode.com/problems/missing-number/)

Solution.java

public class Solution {
  public int missingNumber(int[] nums) {
    for (int num : nums) {
      jump(num, nums);
    }
    for (int i = 0; i < nums.length; i++) {
      if (nums[i] != -1) return i;
    }
    return nums.length;
  }

  private void jump(int num, int[] nums) {
    if (num == -1) return;
    if (num == nums.length) return;
    int temp = nums[num];
    nums[num] = -1;
    jump(temp, nums);
  }
}