[LeetCode] Binary Tree Maximum Path Sum

Given a binary tree, find the maximum path sum.

The path may start and end at any node in the tree.

For example:
Given the below binary tree,

       1
      / \
     2   3

 

Return 6.

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     int calLen(TreeNode *root, int &len)
13     {
14         if (root == NULL)
15         {
16             len = 0;
17             return 0;
18         }
19         
20         if (root->left == NULL && root->right == NULL)
21         {
22             len = root->val;
23             return root->val;
24         }
25         
26         int leftPath, rightPath;
27         int leftLen;
28         if (root->left)
29             leftLen = calLen(root->left, leftPath);
30         else
31         {
32             leftLen = INT_MIN;
33             leftPath = 0;
34         }
35         
36         int rightLen;
37         if (root->right)
38             rightLen = calLen(root->right, rightPath);
39         else
40         {
41             rightLen = INT_MIN;
42             rightPath = 0;
43         }
44         
45         len = max(max(leftPath, rightPath) + root->val, root->val);
46         int maxLen = max(root->val, max(leftPath + rightPath + root->val, 
47             max(leftPath + root->val, rightPath + root->val)));
48         
49         return max(max(leftLen, rightLen), maxLen);
50     }
51     
52     int maxPathSum(TreeNode *root) {
53         // Start typing your C/C++ solution below
54         // DO NOT write int main() function
55         int len;
56         return calLen(root, len);
57     }
58 };
posted @ 2012-12-02 14:05  chkkch  阅读(2791)  评论(0)  编辑  收藏  举报