The article was initially posted on 2017-12-22.
Description
Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
For example:
Given the below binary tree and sum = 22,
5
/ \
4 8
/ / \
11 13 4
/ \ \
7 2 1
return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
Solution
my naive solution (6 ms)
大概的思路就是递归下去，每次传下去的子问题的 sum 要减去当前结点的值。
没预料到有负数，不好剪枝。
Source Code
submission
bool hasPathSum(struct TreeNode *root, int sum) {
if (root == NULL) {
return false;
} else if (root->val == sum && root->left == NULL && root->right == NULL) {
return true;
}
return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);
}