LeetCode之Sum of Left Leaves

Find the sum of all left leaves in a given binary tree.

Example:

   

    

     

      

     
     

      

        3
      
     
    

     

      

     
     

      

          / \
      
     
    

     

      

     
     

      

         9  20
      
     
    

     

      

     
     

      

        /  \
      
     
    

     

      

     
     

      

          15   7
      
     
    

     

      

     
     

      
 
      
     
    

     

      

     
     

      

       There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.
      
     
   
  

   

    

     

      

     
     

      

       /**
      
     
    

     

      

     
     

      

        * 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 sumOfLeftLeaves(TreeNode head) {
      
     
    

     

      

     
     

      

        if (head == null) return 0;
      
     
    

     

      

     
     

      

       		int left = 0, right = 0;
      
     
    

     

      

     
     

      

       		if (head.left != null && head.left.left == null && head.left.right == null) {
      
     
    

     

      

     
     

      

       			left = head.left.val;
      
     
    

     

      

     
     

      

       		} else {
      
     
    

     

      

     
     

      

       			left = sumOfLeftLeaves(head.left);
      
     
    

     

      

     
     

      

       		}
      
     
    

     

      

     
     

      

       		right = sumOfLeftLeaves(head.right);
      
     
    

     

      

     
     

      

       		return left + right;
      
     
    

     

      

     
     

      

        }
      
     
    

     

      

     
     

      

       }