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Day-2 Binary Tree Level Order Traversal II
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Day-2 Binary Tree Level Order Traversal II
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/**
* 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;
* }
* }
*/
class Solution {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> result=new ArrayList<>();
if(root==null) return result;
Queue<TreeNode> st=new LinkedList<>();
st.add(root);
int count=1;
while(!st.isEmpty()){
List<Integer> l=new ArrayList<>();
int num=0;
while(count-->0){
TreeNode t=st.remove();
if(t.left!=null){
st.add(t.left);
num++;
}
if(t.right!=null){
st.add(t.right);
num++;
}
l.add(t.val);
}
count=num;
result.add(0,l);
}
return result;
}
}
class Solution {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> result=new ArrayList<>();
if(root==null) return result;
dfs(root,0,result);
return result;
}
void dfs(TreeNode root, int depth,List<List<Integer>> result){
if(root==null) return;
if(result.size()==depth){
result.add(0,new ArrayList<>());
}
result.get(result.size()-depth-1).add(root.val);
dfs(root.left,depth+1,result);
dfs(root.right,depth+1,result);
}
}