給定一個二叉樹

 示例:

輸入: [1,null,2,3]  
   1
    \
     2
    /
   3 

輸出: [1,2,3]

#include <stdio.h>

struct node {
    struct node *left;
    struct node *right;
    int val;
};

void PreOrderTraversal(struct node *root) {
    if (root == NULL) {
        return;
    }
    printf("%d\n", root->val);
    PreOrderTraversal(root->left);
    PreOrderTraversal(root->right);
}

int main() {
    struct node a, b, c;
    a.val = 1;
    b.val = 2;
    c.val = 3;
	a.left = NULL;
	a.right = &b;
	b.right = NULL;
	b.left = &c;
	c.left = c.right = NULL;
    PreOrderTraversal(&a);
}
 

中序遍歷

#include <stdio.h>

struct node {
    struct node *left;
    struct node *right;
    int val;
};

void InOrderTraversal(struct node *root) {
    if (root == NULL) {
        return;
    }
    InOrderTraversal(root->left);
    printf("%d\n", root->val);
    InOrderTraversal(root->right);
}

int main() {
    struct node a, b, c;
    a.val = 1;
    b.val = 2;
    c.val = 3;
	a.left = NULL;
	a.right = &b;
	b.right = NULL;
	b.left = &c;
	c.left = c.right = NULL;

    InOrderTraversal(&a);
}
 

後序遍歷

#include <stdio.h>

struct node {
    struct node *left;
    struct node *right;
    int val;
};

void PostOrderTraversal(struct node *root) {
    if (root == NULL) {
        return;
    }
    PostOrderTraversal(root->left);
    PostOrderTraversal(root->right);
    printf("%d\n", root->val);
}

int main() {
    struct node a, b, c;
    a.val = 1;
    b.val = 2;
    c.val = 3;
	a.left = NULL;
	a.right = &b;
	b.right = NULL;
	b.left = &c;
	c.left = c.right = NULL;

    PostOrderTraversal(&a);
}