Find Bottom Left Tree Value

Given a binary tree, find the leftmost value in the last row of the tree.

BFS

Time Complexity

思路

If you fully understand how bfs works, it is a really easy problem. Just add one line into the regular bfs template. if(i == 0) leftMost = cur;The leftmost will update until the last level.

代码

public int findBottomLeftValue(TreeNode root) {    //corner case    if(root == null) return 0;    Queue
    
      queue = new LinkedList
     
      ();    queue.offer(root);    TreeNode leftMost = null;    while(!queue.isEmpty()){        int size = queue.size();        for(int i = 0; i < size; i++){            TreeNode cur = queue.poll();            if(i == 0) leftMost = cur;            if(cur.left != null) queue.offer(cur.left);            if(cur.right != null) queue.offer(cur.right);        }    }    return leftMost.val;}