PROBLEM DESCRIPTION
Two elements of a binary search tree (BST), represented by root A are swapped by mistake. Tell us the 2 values swapping which the tree will be restored.
interviewbit
SOLUTION
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class Pair{
int x;
int y;
Pair(int x, int y){
this.x = x;
this.y = y;
}
}
public class Solution {
public ArrayList<Integer> recoverTree(TreeNode A) {
ArrayList<Pair> list = new ArrayList<>();
ArrayList<Integer> inorder = new ArrayList<>();
inorder(A, inorder);
if(inorder.size() <= 1) return null;
for(int i=1; i<inorder.size(); i++){
if(inorder.get(i) < inorder.get(i-1)){
Pair p = new Pair(inorder.get(i-1), inorder.get(i));
list.add(p);
}
}
ArrayList<Integer> ans = new ArrayList<>();
if(list.size() == 1){
ans.add(list.get(0).y);
ans.add(list.get(0).x);
return ans;
}
ans.add(list.get(1).y);
ans.add(list.get(0).x);
return ans;
}
public void inorder(TreeNode root, List<Integer> list){
if(root == null) return;
inorder(root.left, list);
list.add(root.val);
inorder(root.right, list);
}
}