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题目: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.
Example:
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.
解题思路:简单的递归,用心感受就好,注意写好递归的结束条件
代码:
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
int ans = 0;
public int sumNumbers(TreeNode root) {
sum(root,0);
return ans;
}
public void sum(TreeNode root,int curSum){
if(root == null) return;
if(root.left == null && root.right == null)
ans+= curSum*10+root.val;
sum(root.left,curSum*10+root.val);
sum(root.right,curSum*10+root.val);
}