LeetCode 129. Sum Root to Leaf Numbers 解题报告

129. Sum Root to Leaf Numbers

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Total Accepted: 69249  Total Submissions: 216443  Difficulty: Medium

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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    求一棵二叉树所有从根到叶子所表示的数字的和。DFS深搜求解。

    我的AC代码

public class SumRoottoLeafNumbers {

	static int sum = 0;
	
	public static void main(String[] args) {
		TreeNode n1 = new TreeNode(9);
		TreeNode n2 = new TreeNode(1);
		n1.left = n2;

		System.out.println(sumNumbers(n1));
	}

	public static int sumNumbers(TreeNode root) {
        if(root == null) return 0;
        sum = 0;
        dfs(root, 0);
        return sum;
    }
	
	private static void dfs(TreeNode root, int parent) {
		if(root.left == null && root.right == null) {
			sum += (parent * 10 + root.val);
			return;
		}
		parent = parent * 10 + root.val;
		if(root.left != null)	dfs(root.left, parent);
		if(root.right != null)	dfs(root.right, parent);
	}
}