979.txt

思路：
注意负数和正数



代码：


/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    int res=0;
    public int distributeCoins(TreeNode root) {
        dfs(root);
        return res;
    }
    
    public int dfs(TreeNode root){
        if(root==null)return 0;
        
        int l=dfs(root.left);
        int r=dfs(root.right);
        
        int cur=root.val;
        
        cur+=(l+r);
        cur--;
        res+=Math.abs(cur);
        return cur;
        
    }
}