Sum Root to Leaf Numbers

最新推荐文章于 2019-08-12 13:35:43 发布

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最新推荐文章于 2019-08-12 13:35:43 发布

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原文链接：http://www.cnblogs.com/RazerLu/p/3536938.html

本文介绍了一种算法，用于求解二叉树中所有从根节点到叶子节点的路径所表示数字的总和。通过深度优先搜索遍历二叉树，并记录下每条路径的数值，最终返回所有路径数值的总和。

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
    }
}

转载于:https://www.cnblogs.com/RazerLu/p/3536938.html