leetCode(40):Path Sum
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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.
/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: bool findPath(TreeNode* root, int nowSum,const int sum) { nowSum += root->val;//当前值 //假设已经是叶子结点,且和相等,则直接返回真 if (!root->left && !root->right && nowSum == sum) return true; bool found_left = false; bool found_right = false; if (root->left) //左子树不为空。则在左子树中搜索 found_left = findPath(root->left, nowSum, sum); if (!found_left && root->right) //假设左子树没找到,则在右子树中搜索 found_right = findPath(root->right, nowSum, sum); return found_left || found_right;//仅仅要在一条支中上找到则返回真 } bool hasPathSum(TreeNode* root, int sum) { if (root == NULL) return false; findPath(root, 0, sum); } };
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