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,
For example:
Given the below binary tree,
1
/ \
2 3
Return 6
.
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
#define IMAX(x,y) (x>y?x:y)
int maxPathSum(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if (!root)
{
return 0;
}
int left_sum = maxPathSum(root->left);
int right_sum = maxPathSum(root->right);
int sum = left_sum + root->val + right_sum;
int m = IMAX(left_sum,right_sum);
return IMAX(m,sum);
}
};//the code above is wrong,think about it why?//we must keep the record maximum with root node,even if it is may not the whole max sum//below is the right code refer to [remlosttime]'s code
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
//we must return the max and the maximum path with root node
int maxPathWithRoot(TreeNode * root,int &sum_with_root){
if (!root){
sum_with_root = 0;
return 0;
}
if (!root->left && !root->right){
sum_with_root = root->val;
return root->val;
}
int left_max_sum = 0,left_with_root_max_sum = 0;
int right_max_sum = 0,right_with_root_max_sum = 0;
if (root->left){
left_max_sum = maxPathWithRoot(root->left,left_with_root_max_sum);
}else{
left_max_sum = INT_MIN;
left_with_root_max_sum = 0;
}
if (root->right){
right_max_sum = maxPathWithRoot(root->right,right_with_root_max_sum);
}else{
right_max_sum = INT_MIN;
right_with_root_max_sum = 0;
}
sum_with_root = max(left_with_root_max_sum + root->val,
max(right_with_root_max_sum + root->val,root->val));
int sum = max(sum_with_root,
left_with_root_max_sum + right_with_root_max_sum + root->val);
return max(sum,max(left_max_sum,right_max_sum));
}
int maxPathSum(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int sum_with_root;
return maxPathWithRoot(root,sum_with_root);
}
};
原文链接: https://www.cnblogs.com/kwill/archive/2013/02/13/2910685.html
欢迎关注
微信关注下方公众号,第一时间获取干货硬货;公众号内回复【pdf】免费获取数百本计算机经典书籍
原创文章受到原创版权保护。转载请注明出处:https://www.ccppcoding.com/archives/77899
非原创文章文中已经注明原地址,如有侵权,联系删除
关注公众号【高性能架构探索】,第一时间获取最新文章
转载文章受原作者版权保护。转载请注明原作者出处!