129. Sum Root to Leaf Numbers

最新推荐文章于 2020-12-22 20:22:53 发布

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本文介绍了一种算法问题——求解二叉树中所有从根节点到叶子节点的路径数值之和，并提供了详细的Java代码实现。通过递归遍历的方法，文章展示了如何将每个路径转换为数字并计算总和。

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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.

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Solution:

Tips:

tree, recursion

Java Code:

/**
 * 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 sumNumbers(TreeNode root) {
        if (null == root) {
            return 0;
        }
        
        int[] sum = {0};
        sumNumbers(root, "", sum);
        
        return sum[0];
    }
    
    private void sumNumbers(TreeNode root, String s, int[] sum) {
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            sum[0] += Integer.valueOf(s + root.val);
        }
        
        if (root.left != null) {
            sumNumbers(root.left, s + root.val, sum);
        }
        if (root.right != null) {
            sumNumbers(root.right, s + root.val, sum);
        }
    }
}