题解 | #二叉树的前序遍历#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

void preorder(int* ret, struct TreeNode* root, int *returnSize){
    if(root == NULL){
        return ;
    }

    ret[(*returnSize)++]  = root->val;
    preorder(ret, root->left, returnSize);
    preorder(ret, root->right, returnSize);
}

/**
 * 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* preorderTraversal(struct TreeNode* root, int* returnSize ) {
    // write code here
    int * ret = (int*)malloc(sizeof(int) * 100);
    *returnSize = 0;
    preorder(ret,root, returnSize);
    return ret;
}