力扣刷题记录 -- JAVA--48---404. 左叶子之和

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一、题目

二、代码

/**
 * 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 int sumOfLeftLeaves(TreeNode root) 
    {
       if(root == null) return 0;
       int return_num = 0;
       Queue<TreeNode> queue = new LinkedList<>();
       queue.offer(root); 
       while(!queue.isEmpty())
       {
            int i;
            int length = queue.size();
            for(i=0;i<length;i++)
            {
               TreeNode temp_node= queue.poll();
                if(temp_node.left!=null) 
                {
                    queue.offer(temp_node.left);
                    if(temp_node.left.left==null&&temp_node.left.right==null)
                    {
                        return_num = return_num+temp_node.left.val;
                        System.out.println("加上  "+temp_node.left.val);
                    }
                }
                if(temp_node.right!=null)
                {
                   queue.offer(temp_node.right);
                      
                }
            }
       
       }
       return return_num;


    }
} 

三、运行结果