LeetCode 129 Sum Root to Leaf Numbers(递归求和)
2017-07-12 20:04
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Given a binary tree containing digits from
each root-to-leaf path could represent a number.
An example is the root-to-leaf path
represents the number
Find the total sum of all root-to-leaf numbers.
For example,
The root-to-leaf path
The root-to-leaf path
Return the sum = 12 + 13 =
题目大意:给出一个二叉树,从根节点到叶节点的一条路径上的所有数字组成一个数字。例如1->2->3是一条从根节点到叶节点的一条路径,那么这条路径代表的数字就是123。求出所有从根节点到叶节点的路径所代表的数字之和。
解题思路:当一个节点同时没有左右子树的时候返回,否则递归处理它的左右子树。
代码如下:
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
static int getPathSum(struct TreeNode* root, int sum) {
if(!root) return 0;
sum = 10 * sum + root->val;
if(!root->left && !root->right) return sum;
return getPathSum(root->left, sum) + getPathSum(root->right, sum);
}
int sumNumbers(struct TreeNode* root) {
return getPathSum(root, 0);
}
0-9only,
each root-to-leaf path could represent a number.
An example is the root-to-leaf path
1->2->3which
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->2represents the number
12.
The root-to-leaf path
1->3represents the number
13.
Return the sum = 12 + 13 =
25.
题目大意:给出一个二叉树,从根节点到叶节点的一条路径上的所有数字组成一个数字。例如1->2->3是一条从根节点到叶节点的一条路径,那么这条路径代表的数字就是123。求出所有从根节点到叶节点的路径所代表的数字之和。
解题思路:当一个节点同时没有左右子树的时候返回,否则递归处理它的左右子树。
代码如下:
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
static int getPathSum(struct TreeNode* root, int sum) {
if(!root) return 0;
sum = 10 * sum + root->val;
if(!root->left && !root->right) return sum;
return getPathSum(root->left, sum) + getPathSum(root->right, sum);
}
int sumNumbers(struct TreeNode* root) {
return getPathSum(root, 0);
}
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