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  • Sum Root to Leaf Numbers

    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.

    /**
     * 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) {
            ArrayList<Integer> result = new ArrayList<Integer>();
            if(root == null) return 0;
            dfs(result, 0, root);
            int sum = 0;
            for(int i : result){
                sum += i;
            }
            
            return sum;
        }
        
        private void dfs(ArrayList<Integer> result, int currentNumber, TreeNode root){
            if(root.left == null && root.right == null){
                result.add(10*currentNumber+root.val);
            }
            
            currentNumber = currentNumber*10+root.val;
            
            if(root.left != null){
                dfs(result, currentNumber, root.left);
            }
            if(root.right != null){
                dfs(result, currentNumber, root.right);
            }
       // number是值传递,所以不用-1 } }
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  • 原文地址:https://www.cnblogs.com/RazerLu/p/3536938.html
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