Problem

Given a binary tree, return the tilt of the whole tree.

The tilt of a tree node is defined as the absolute difference between the sum of all left subtree node values and the sum of all right subtree node values. Null node has tilt 0.

The tilt of the whole tree is defined as the sum of all nodes' tilt.

Example

一個(gè)例子

Solution

/**
 * 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:
    int tilt = 0;
    int findTilt(TreeNode* root) {
        traverse(root);
        return tilt;
    }
    
    int traverse(TreeNode* root)
    {
        if (root == NULL) return 0;
        int left = traverse(root->left);
        int right = traverse(root->right);
        tilt += abs(left-right);
        return left+right+root->val;
    }
};

簡單的分治的思想就可以解決這個(gè)問題。