int maxPathSumHelper(TreeNode * node, int &curMax) {
if (!node)
return INT_MIN;
int cur = node->val;
int left = maxPathSumHelper(node->left,curMax);
int right = maxPathSumHelper(node->right,curMax);
int maxSubTree = (left < right?right:left);
// get max of
// any sub tree and current node
// left-node-right
// return cur + maxSubTree
if (node->val > curMax) curMax = node->val;
if (left > curMax) curMax = left;
if (right > curMax) curMax = right;
if (node->left)
cur += left;
if (node->right)
cur += right;
if (cur > curMax) curMax = cur;
cur = node->val;
if (maxSubTree > 0)
cur += maxSubTree;
return cur;
}
void maxPathSumHelper(TreeNode *node, int &csum, int &maxsum) {
if (!node) {
csum = 0;
return;
}
int lsum = 0, rsum = 0;
maxPathSumHelper(node->left, lsum, maxsum);
maxPathSumHelper(node->right, rsum, maxsum);
csum = max(node->val, max(node->val + lsum, node->val + rsum));
maxsum = max(maxsum, max(csum, node->val + lsum + rsum));
}
void maxPathSumHelper (Node* node, int& csum, int& maxsum)
{
if (!node) {
csum = 0;
return;
}
int lsum = 0, rsum = 0;
//get the left tree max
maxPathSumHelper (node->left, lsum, maxsum);
//get the right tree max
maxPathSumHelper (node->right, rsum, maxsum);
//get the bigger one of left or right tree, Note that the first comparison is needed if there are negative nodes in the tree
csum = std::max (node->val, std::max (node->val + lsum, node->val + rsum) );
//if the tree go throuh a root, there is a potential max sum too
maxsum = std::max (maxsum, std::max (csum, node->val + lsum + rsum) );
}
int maxPathSum (Node* root)
{
int csum = 0;
int maxsum = -1;
maxPathSumHelper (root, csum, maxsum);
return maxsum;
}
int maxPathSum(TreeNode *root) {
if(!root)
return 0;
int curMax = INT_MIN;
int sum = maxPathSumHelper(root, curMax);
return max(sum,curMax);
}
int maxPathSum(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int csum;
int maxsum = INT_MIN;
maxPathSumHelper(root, csum, maxsum);
return maxsum;
}
int maxPathSum(TreeNode *root) {
int csum;
int maxSum = INT32_MIN;
maxPathSumHelper(root, csum, maxsum);
return maxSum;
}
