题目
给定一个二叉树,返回其按层次遍历的节点值。 (即逐层地,从左到右访问所有节点)。
例如:
给定二叉树: [3,9,20,null,null,15,7],
3
/ \
9 20
/ \
15 7
返回其层次遍历结果:
[
[3],
[9,20],
[15,7]
]
题解
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
/**
* Return an array of arrays of size *returnSize.
* The sizes of the arrays are returned as *columnSizes array.
* Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
*/
int get_depth(struct TreeNode *root) {
if (root == NULL) {
return 0;
}
int ldepth = get_depth(root->left) + 1;
int rdepth = get_depth(root->right) + 1;
rdepth > ldepth && (ldepth = rdepth);
return ldepth;
}
void get_size(struct TreeNode *root, int *columnSizes, int level) {
if (root == NULL) {
return ;
}
++columnSizes[level];
get_size(root->left, columnSizes, level + 1);
get_size(root->right, columnSizes, level + 1);
}
void get_val(struct TreeNode *root, int *columnSizes, int **data, int level) {
if (root == NULL) {
return ;
}
data[level][columnSizes[level]++] = root->val;
get_val(root->left, columnSizes, data, level + 1);
get_val(root->right, columnSizes, data, level + 1);
}
int** levelOrder(struct TreeNode *root, int **columnSizes, int *returnSize) {
*returnSize = get_depth(root);
*columnSizes = (int *)calloc((*returnSize), sizeof(int));
int **data = (int **)malloc(sizeof(int *) * (*returnSize));
get_size(root, *columnSizes, 0);
for (int i = 0; i < *returnSize; i++) {
data[i] = (int *)malloc(sizeof(int ) * (*columnSizes)[i]);
(*columnSizes)[i] = 0;
}
get_val(root, *columnSizes, data, 0);
return data;
}