原题：
Given the root of a binary tree, then value v and depth d, you need to add a row of nodes with value v at the given depth d. The root node is at depth 1.
The adding rule is: given a positive integer depth d, for each NOT null tree nodes N in depth d-1, create two tree nodes with value v as N's left subtree root and right subtree root. And N's original left subtree should be the left subtree of the new left subtree root, its original right subtree should be the right subtree of the new right subtree root. If depth d is 1 that means there is no depth d-1 at all, then create a tree node with value v as the new root of the whole original tree, and the original tree is the new root's left subtree.
Example 1:
Input: A binary tree as following: 4 / \ 2 6 / \ / 3 1 5 v = 1 d = 2 Output: 4 / \ 1 1 / \ 2 6 / \ / 3 1 5
Example 2:
Input: A binary tree as following: 4 / 2 / \ 3 1 v = 1 d = 3 Output: 4 / 2 / \ 1 1 / \ 3 1
Note:
The given d is in range [1, maximum depth of the given tree + 1].The given binary tree has at least one tree node. 代码如下： /** * Definition for a binary tree node. * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * }; */ struct TreeNode* addOneRow(struct TreeNode* root, int v, int d) { if(d==1) { struct TreeNode* newroot; newroot=(struct TreeNode*)malloc(sizeof(struct TreeNode)); newroot->val=v; newroot->left=root; newroot->right=NULL; return newroot; } if(d==2) { struct TreeNode* left; struct TreeNode* right; left=(struct TreeNode*)malloc(sizeof(struct TreeNode)); right=(struct TreeNode*)malloc(sizeof(struct TreeNode)); left->val=v; right->val=v; left->left=root->left; left->right=NULL; right->right=root->right; right->left=NULL; root->left=left; root->right=right; } else { if(root->left!=NULL) addOneRow(root->left,v,d-1); if(root->right!=NULL) addOneRow(root->right,v,d-1); } return root; } 还是一种递归，只不过是那种分支递归？反正写起来不是很难。有要交流算法的童鞋，可以留言，加微信或者微信讨论下。
