Tree树

tree，是非线性数据结构，array、linked list、stack、queue，是线性数据结构。

线性数据结构：数据元素是一对一

非线性数据结构：数据元素存在一对多或者多对一的关系

#include<stdio.h>
#include<stdlib.h>

struct tree
{
    int data;
    struct tree * left;
    struct tree * right;
};
struct tree * newNode(int data)
{
    struct tree * root = (struct tree *)malloc(sizeof(struct tree));
    root->data = data;
    root->left = NULL;
    root->right = NULL;

    return root;
}
void printLevelOrder(struct tree * root)
{
    int height = getHeight(root);

    printf("%d
", height);
    for(int i = 1; i <= height; i++)
    {
        printGivenLevel(root, i);
    }
}
void printGivenLevel(struct tree * root, int level)
{
    if(NULL == root)
    {
        return ;
    }
    if(1 == level)
    {
        printf("%d  ", root->data);
    }
    else if(level > 1)
    {
        printGivenLevel(root->left, level-1);
        printGivenLevel(root->right, level-1);
    }
}
int getHeight(struct tree * root)
{
    int lheight = 0;
    int rheight = 0;

    if(NULL == root)
    {
        return 0;
    }
    else
    {
        //两个递归有点恶心，头脑混乱的话，最好调试下，屡一下
        lheight = getHeight(root->left);
        rheight = getHeight(root->right);

        if(lheight > rheight)
        {
            return (lheight + 1);
        }
        else
        {
            return (rheight + 1);
        }
    }
}
int main(void)
{
    struct tree * root = newNode(1);
    root->left = newNode(2);
    root->right = newNode(3);
    root->left->left = newNode(4);
    root->left->right = newNode(5);

    printLevelOrder(root);
    return 0;
}