BiruLyu
7/3/2017 - 5:28 PM

## 513. Find Bottom Left Tree Value(BFS).java

``````/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
private int bottomLeftValue = -1;
private int maxDepth = 0;
public int findBottomLeftValue(TreeNode root) {
if (root == null) {
return -1;
}
dfsHelper(root, 1);
return bottomLeftValue;
}

private void dfsHelper(TreeNode root, int depth) {
if (root == null) {
return;
}

if (depth > maxDepth) {
//update the result;
maxDepth = depth;
bottomLeftValue = root.val;
}
dfsHelper(root.left, depth + 1);
dfsHelper(root.right, depth + 1);
}
}``````
``````/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int findBottomLeftValue(TreeNode root) {
queue.offer(root);
int left = -1;
while (!queue.isEmpty()) {
int curSize = queue.size();
for (int i = 0; i < curSize; i++) {
TreeNode cur = queue.poll();
if (i == 0) left = cur.val;
if (cur.left != null) queue.offer(cur.left);
if (cur.right != null) queue.offer(cur.right);
}
}
return left;
}
}``````