二叉树的最大子树和

原文出处：http://blog.csdn.net/brucehb/article/details/12322927

给一个二叉树，每个节点都是正或负整数，求该二叉树的最大子树和？

struct TreeNode  {      int val;      TreeNode *left;      TreeNode *right;  };    int visit(TreeNode *root, int &result)  {      if (root == NULL)      {          return 0;      }        int sum = root->val;      if (root->left != NULL || root->right != NULL)      {          int left = visit(root->left, result);          int right = visit(root->right, result);          sum += left + right;            result = max(sum, result);      }        return sum;  }    int maxSum(TreeNode *root)  {      int result = INT_MIN;      visit(root, result);        return result;  }