Delete Node in a BST LeetCode solution in Java

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class Solution {
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  public TreeNode deleteNode(TreeNode root, int key) {
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    if (root == null) return null;
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    if (key < root.val) {
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      root.left = deleteNode(root.left, key);
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      return root;
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    } else if (key > root.val) {
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      root.right = deleteNode(root.right, key);
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      return root;
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    } else {
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      if (root.left == null) {
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        return root.right;
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      } else if (root.right == null) {
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        return root.left;
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      } else {
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        TreeNode min = root.right;
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        while (min.left != null) {
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          min = min.left;
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        }
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        root.val = min.val;
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        root.right = deleteNode(root.right, min.val);
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        return root;
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      }
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    }
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  }
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}