LeetCode 112:Path Sum

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.

//利用深度优先搜索DFS，当搜索到的节点为叶子节点时。才推断总和是否等于给定的sum值
class Solution {
public:
bool dfs(TreeNode* node, int sum, int curSum){
if (node == NULL)
return false;
if (node->left == NULL && node->right == NULL)
return curSum + node->val == sum;

return dfs(node->left, sum, curSum + node->val) || dfs(node->right, sum, curSum + node->val);
}

bool hasPathSum(TreeNode* root, int sum) {
return dfs(root, sum, 0);
}
};