資訊專(zhuān)欄INFORMATION COLUMN
摘要：解題思路本題要求所有從根結(jié)點(diǎn)到葉子節(jié)點(diǎn)的路徑和，我們用遞歸實(shí)現(xiàn)。結(jié)束條件當(dāng)遇到葉子節(jié)點(diǎn)時(shí)，直接結(jié)束，返回計(jì)算好的如果遇到空節(jié)點(diǎn)，則返回?cái)?shù)值。
Sum Root to Leaf Numbers
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.
解題思路
本題要求所有從根結(jié)點(diǎn)到葉子節(jié)點(diǎn)的路徑和，我們用遞歸實(shí)現(xiàn)。
結(jié)束條件：當(dāng)遇到葉子節(jié)點(diǎn)時(shí)，直接結(jié)束，返回計(jì)算好的sum;如果遇到空節(jié)點(diǎn)，則返回?cái)?shù)值0。
2.代碼
public class Solution {
public int sumNumbers(TreeNode root) {
return sum(root,0);
}
private int sum(TreeNode root, int cur){
if(root==null) return 0;
cur=10*cur+root.val;
if(root.left==null&&root.right==null)
return cur;
else
return sum(root.left,cur)+sum(root.right,cur);
}
}
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