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  • LeetCode :: Sum Root to Leaf Numbers [tree、dfs]

    Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

    An example is the root-to-leaf path 1->2->3 which represents the number 123.

    Find the total sum of all root-to-leaf numbers.

    For example,

        1
       / 
      2   3
    

    The root-to-leaf path 1->2 represents the number 12.
    The root-to-leaf path 1->3 represents the number 13.

    Return the sum = 12 + 13 = 25.


    从根节点開始,dfs的思路,事实上也就是postorder(先序遍历),遍历路径上的值每次乘以基数10,过程非常easy,代码例如以下:

    class Solution {
    public:
        int sum;
        
        void dfs(TreeNode *root, int pre){
            if (root == NULL)
                return;
                
            int current = root->val + 10 * pre;
            if (root->left == NULL && root->right == NULL){
                sum += current;
                return;
            }
            
            if (root->left)
                dfs(root->left, current);
            if (root->right)
                dfs(root->right, current);
        }
        
        int sumNumbers(TreeNode *root) {
            sum = 0;
            dfs(root, 0);
            return sum;
        }
    };


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  • 原文地址:https://www.cnblogs.com/claireyuancy/p/6770504.html
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