[leeccode] Path Sum

原创于 2015-06-07 13:53:31 发布 · 351 阅读

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本文探讨了LeetCode中路径总和问题的解决方案。通过递归方法遍历二叉树的所有根到叶子节点路径，判断是否存在一条路径使得路径上所有节点值之和等于给定的目标值。示例中给出了具体的二叉树结构及求解过程。

From : https://leetcode.com/problems/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.

/**
 * 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) {
        return find(root, sum, 0);
    }
    bool find(TreeNode* node, int sum, int cur) {
        if(!node) return false;
        if(!node->left && !node->right) return node->val+cur == sum;
		return find(node->left, sum, node->val+cur) || find(node->right, sum, node->val+cur);
    }
};