[LeetCode 129] Sum Root to Leaf Numbers

题目链接：sum-root-to-leaf-numbers

import java.util.LinkedList;


/**
 * 
		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.
 *
 */

public class SumRootToLeafNumbers {

	public class TreeNode {
		int val;
		TreeNode left;
		TreeNode right;

		TreeNode(int x) {
			val = x;
		}
	}

	//递归版
	
//	109 / 109 test cases passed.
//	Status: Accepted
//	Runtime: 215 ms
//	Submitted: 0 minutes ago

	 public int sumNumbers(TreeNode root) {
		 return dfs(root, 0);
	 }
	 public int dfs(TreeNode root, int sum) {
		 if(root == null) return 0;
		 if(root.left == null && root.right == null) return root.val + sum * 10;		 
		 return dfs(root.left, root.val + sum * 10) + dfs(root.right, root.val + sum * 10);		 
	 }
	
	//层次遍历法
	
//	109 / 109 test cases passed.
//	Status: Accepted
//	Runtime: 234 ms
//	Submitted: 0 minutes ago

	
    public int sumNumbers1(TreeNode root) {
    	int sum = 0;
    	if(root == null) return sum;
    	LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
    	queue.add(root);
    	while(!queue.isEmpty()) {
    		int levelLen = queue.size();    		
    		for (int i = 0; i < levelLen; i++) {
				TreeNode node = queue.removeFirst();
				if(node.left == null && node.right == null)
					sum += node.val;
				if(node.left != null) {
					node.left.val += node.val * 10;
					queue.add(node.left);
				}
				if(node.right != null) {
					node.right.val += node.val * 10;
					queue.add(node.right);
				}
			}
    	}
    	return sum;
    }
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub

	}

}

[LeetCode 129] Sum Root to Leaf Numbers

原文：http://blog.csdn.net/ever223/article/details/44544217