LeetCode 112:Path Sum

原创于 2015-12-22 12:50:32 发布 · 1.5k 阅读

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本文介绍了一种通过深度优先搜索（DFS）算法来判断给定的二叉树中是否存在从根节点到叶子节点的路径，使得路径上的节点值之和等于给定的目标值的方法。

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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.

 //利用深度优先搜索DFS，当搜索到的节点为叶子节点时，才判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);
	}
};