题解 | #二叉树的前序遍历#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param root TreeNode类 
 * @return int整型一维数组
 * @return int* returnSize 返回数组行数
 */
int TreeSize(struct TreeNode* root)
 {
    if(root==NULL)
        return 0;
    return TreeSize(root->left) + TreeSize(root->right)+1;
 }
 void Pre_Order(struct TreeNode*root,int*i,int*arr)
 {
    if(root==NULL)
          return;
    arr[(*i)++] = root->val;
    Pre_Order(root->left,i,arr);
    Pre_Order(root->right,i,arr);
 }
int* preorderTraversal(struct TreeNode* root, int* returnSize) 
{
   *returnSize = TreeSize(root);//先获取要开的数组大小
   int*arr = (int*)malloc(sizeof(int)*(*returnSize));
   int i = 0;
   Pre_Order(root,&i,arr);
   return arr;
}