【leetcode刷题】T123-路径总和

示例: 
给定如下二叉树，以及目标和 sum = 22，
              5
             / \
            4   8
           /   / \
          11  13  4
         /  \      \
        7    2      1
返回 true, 因为存在目标和为 22 的根节点到叶子节点的路径 5->4->11->2。

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def hasPathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: bool
        """
        if not root:
            return False
        if not root.left and not root.right:
            return root.val == sum
        if root.left and root.right:
            return self.hasPathSum(root.left, sum-root.val) or self.hasPathSum(root.right, sum-root.val)
        if root.left:
            return self.hasPathSum(root.left, sum-root.val)
        if root.right:
            return self.hasPathSum(root.right, sum-root.val)

/**
 * 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 hasPathSum(TreeNode* root, int sum) {
        if(!root)
            return false;
        if(!root->left && !root->right)
            return root->val == sum;
        if(root->left && root->right)
            return hasPathSum(root->left, sum-root->val) || hasPathSum(root->right, sum-root->val);
        if(root->left)
            return hasPathSum(root->left, sum-root->val);
        return hasPathSum(root->right, sum-root->val);
    }
};