二叉树的前序遍历（力扣

void preOrder(struct TreeNode* q,int* nums,int* ret)
{
    if(!q) return;
    nums[(*ret)++]=q->val;
    preOrder(q->left,nums,ret);
    preOrder(q->right,nums,ret);
}
 
int* preorderTraversal(struct TreeNode* root, int* returnSize) {
   *returnSize=0;
    int* nums=(int*)malloc(102*sizeof(int));
    preOrder(root,nums,returnSize);
    return nums;
}