[LeetCode] 513 - Find Bottom Left Tree Value

題意

找出樹中最下層且最左邊的元素。

解法

BFS。

程式

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var findBottomLeftValue = function(root) {
  if ( !root ) return 0;
  let queue = [root];
  let result = 0;
  while( queue.length !== 0 ){
    let length = queue.length;
    for ( let i = 0; i < length; i ++ ){
      let node = queue.shift();
      if ( i === 0 ) result = node.val;
      if ( node.left ) queue.push(node.left);
      if ( node.right ) queue.push(node.right);
    }
  }
  return result;
};