[637] Average of Levels in Binary Tree

有一陣子沒寫tree，很意外竟然自己寫出來XD （所以人家是easy XD!）

對於tree的深度沒有考慮清楚，如果是超級不balance那可能很歪，以上。

/**

* Definition for a binary tree node.

* struct TreeNode {

* int val;

* struct TreeNode *left;

* struct TreeNode *right;

* };

*/

/**

* Note: The returned array must be malloced, assume caller calls free().

*/

#define MAX(A,B) (A>B)?(A):(B)

int calculate(struct TreeNode* root, int level, double *ret, int *count)

{

if (root == NULL)

return level;

ret[level]+= root->val;

count[level]++;

int left = calculate(root->left, level+1, ret, count);

int right = calculate(root->right, level+1, ret, count);

return MAX(left, right);

}

double* averageOfLevels(struct TreeNode* root, int* returnSize) {

double *ret = calloc (10000, sizeof(double));

int *count = calloc (10000, sizeof(int));

int level = calculate(root, 0, ret, count);

for (int i=0;i<level;i++)

ret[i]/=count[i];

*returnSize = level;

return ret;

}