Repository navigation
Expand file tree
/
Copy pathSumRoottoLeafNumbers.java
More file actions
84 lines (78 loc) · 2.29 KB
/
Copy pathSumRoottoLeafNumbers.java
File metadata and controls
84 lines (78 loc) · 2.29 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
package com.bytecode.leetcode.tree;
import java.util.Stack;
/**
* 129. Sum Root to Leaf Numbers
* <p>
* Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
* <p>
* An example is the root-to-leaf path 1->2->3 which represents the number 123.
* <p>
* Find the total sum of all root-to-leaf numbers.
* <p>
* Note: A leaf is a node with no children.
* <p>
* Example:
* <p>
* Input: [1,2,3]
* 1
* / \
* 2 3
* Output: 25
* Explanation:
* The root-to-leaf path 1->2 represents the number 12.
* The root-to-leaf path 1->3 represents the number 13.
* Therefore, sum = 12 + 13 = 25.
* Example 2:
*
* Input: [4,9,0,5,1]
* 4
* / \
* 9 0
* / \
* 5 1
* Output: 1026
* Explanation:
* The root-to-leaf path 4->9->5 represents the number 495.
* The root-to-leaf path 4->9->1 represents the number 491.
* The root-to-leaf path 4->0 represents the number 40.
* Therefore, sum = 495 + 491 + 40 = 1026.
* <p>
* <a href="https://leetcode.com/problems/sum-root-to-leaf-numbers/">129. Sum Root to Leaf Numbers</a>
* <p>
* <a href="https://leetcode-cn.com/problems/sum-root-to-leaf-numbers/">129. 求根到叶子节点数字之和</a>
* <p>
* Created by vencial on 2019-09-10.
*/
public class SumRoottoLeafNumbers {
/**
* 1. 结点入栈, 并把子结点的值与当前结点值*10想加, 再更到子结点中
* 2. 遇到叶子结点, 则计算sum值
* <p>
* 1. push node to stack and update sub tree's value by adding parent's value * 10
* 2. if it's a leaf node, then count the sum
*
* @param root root
* @return int
*/
public int sumNumbers(TreeNode root) {
if (root == null) return 0;
Stack<TreeNode> stack = new Stack<>();
stack.push(root);
int sum = 0;
while (!stack.isEmpty()) {
TreeNode node = stack.pop();
if (node.left != null) {
node.left.val += node.val * 10;
stack.push(node.left);
}
if (node.right != null) {
node.right.val += node.val * 10;
stack.push(node.right);
}
if (node.left == null && node.right == null) {
sum += node.val;
}
}
return sum;
}
}