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InorderSuccessor285.java
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InorderSuccessor285.java
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package Leetcode;
import java.util.List;
import java.util.Stack;
public class InorderSuccessor285 {
/**Method 1: Not Iteration; Time:O(H); Space:O(1)-O(H) **/
public TreeNode inorderSuccessor1(TreeNode root, TreeNode p) {
if(root == null) {
return null;
}
Stack<TreeNode> stack = new Stack<>();
TreeNode cur = root;
boolean flag = false;
while(cur != null || !stack.isEmpty()) {
while(cur != null) {
stack.push(cur);
cur = cur.left;
}
if(!stack.isEmpty()) {
cur = stack.pop();
if(flag) {
return cur;
}
if(cur == p) {
flag = true;
}
}
cur = cur.right;
}
return null;
}
/**Method 2: Recursive; Time:O(H); Space: O(H) **/
public static TreeNode inorderSuccessor2(TreeNode root, TreeNode p) {
if(root == null || p == null) {
return null;
}
if(root.val <= p.val) {
return inorderSuccessor2(root.right, p);
}
TreeNode node = inorderSuccessor2(root.left, p);
if(node != null && node.val < root.val) {
return node;
} else {
return root;
}
}
/**Method 3: Iteration; Time:O(H); Space: O(1) **/
public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
if(root == null || p == null) {
return null;
}
TreeNode cur = root;
TreeNode res = null;
while(cur != null) {
if(cur.val <= p.val) {
cur = cur.right;
} else {
if(res == null || res.val > cur.val) {
res = cur;
}
cur = cur.left;
}
}
return res;
}
//Definition for a binary tree node.
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode() {}
TreeNode(int val) { this.val = val; }
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
}