題目描述：

We are given the head node?root?of a binary tree, where additionally every node's value is either a 0 or a 1.

Return the same tree where every subtree (of the given tree) not containing a 1 has been removed.

(Recall that the subtree of a node X is X, plus every node that is a descendant of X.)

Example 1: Input: [1,null,0,0,1] Output: [1,null,0,null,1]Explanation: Only the red nodes satisfy the property "every subtree not containing a 1". The diagram on the right represents the answer.

Example 2: Input: [1,0,1,0,0,0,1] Output: [1,null,1,null,1]

Example 3: Input: [1,1,0,1,1,0,1,0] Output: [1,1,0,1,1,null,1]

Note:

• The binary tree?will?have?at?most?100 nodes.
• The value of each node will only be?0?or?1.

解題思路：

樹一般用遞歸的方法。

代碼：

1 /** 2 * Definition for a binary tree node. 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 TreeNode* pruneTree(TreeNode* root) { 13 if (root == NULL) 14 return NULL; 15 root->left = pruneTree(root->left); 16 root->right = pruneTree(root->right); 17 if (root->val == 0 && root->left == NULL && root->right == NULL) { 18 free(root); 19 return NULL; 20 } 21 return root; 22 } 23 };

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轉(zhuǎn)載于:https://www.cnblogs.com/gsz-/p/9385599.html

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