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
 */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
static int num;

void preoder(struct TreeNode* root, int* a)
{
    if(root ==  NULL)
        return;
    a[num++] = root->val;
    preoder(root->left,a);
    preoder(root->right,a);
}

int* preorderTraversal(struct TreeNode* root, int* returnSize ) {
    
    //二叉树的节点数量满足 1≤n≤100
    int *a = (int *)malloc(sizeof(int)*100);
    preoder(root,a);
    *returnSize = num;
    return a;
}