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  • 【LeetCode】Sum Root to Leaf Numbers

    题目

    Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

    An example is the root-to-leaf path 1->2->3 which represents the number 123.

    Find the total sum of all root-to-leaf numbers.

    For example,

        1
       / 
      2   3
    

    The root-to-leaf path 1->2 represents the number 12.
    The root-to-leaf path 1->3 represents the number 13.

    Return the sum = 12 + 13 = 25.

    解答

    用树的递归解决

    /**
     * Definition for binary tree
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    public class Solution {
        public int sumNumbers(TreeNode root) {
            if(root==null){
                return 0;
            }
            return sum(root,0);
        }
        
        public int sum(TreeNode node,int parentVal){
            int sum=0;
            int temp=parentVal*10+node.val;
            if(node.left==null&&node.right==null){
                sum=temp;
            }
            if(node.left!=null){
                sum+=sum(node.left,temp);
            }
            if(node.right!=null){
                sum+=sum(node.right,temp);
            }
            return sum;
        }
    } 

    ---EOF---

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  • 原文地址:https://www.cnblogs.com/mengfanrong/p/3841290.html
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