sum-root-to-leaf-numbers-LeetCode

sum-root-to-leaf-numbers

题目描述

Given a binary tree containing digits from0-9only, each root-to-leaf path could represent a number. An example is the root-to-leaf path1->2->3which represents the number123. Find the total sum of all root-to-leaf numbers. For example, 

1
/ \
2 3

The root-to-leaf path1->2represents the number12. The root-to-leaf path1->3represents the number13. Return the sum = 12 + 13 =25.

思路

1. 根据题意，我们可以根据先序遍历的顺序一边遍历一边计算
2. 注意：设置两个值temp和sum，每次进入结点的时候temp加一次，每次从这个节点出来的时候temp减去这个节点的值，遍历到叶子节点的时候要对sum进行一次计算

代码

/**
 * 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) {
    	int[] data = {0, 0}; // {temp, sum}
    	if (root != null) {
    		getSum(root, data);
    	}
    	return data[1];
    	
    }
    public void getSum(TreeNode root, int[] data) {
    	data[0] *= 10;
    	data[0] += root.val;
    	if (root.left == null && root.right == null) {
    		data[1] += data[0];
    		data[0] -= root.val;
    		data[0] /= 10;
    		return;
    	}
    	if (root.left != null) {
    		getSum(root.left, data);
    	}
    	if (root.right != null) {
    		getSum(root.right, data);
    	}
    	data[0] -= root.val;
    	data[0] /= 10;
    }
}