C语言：1、遍历二叉树。 请输入一棵二叉树的扩展的前序序列，经过处理后生成一棵二叉树，然后对于该二叉树输出中序和后序遍历序列。 2、按层次遍历二叉树。

好的，我可以帮你解决这个问题。

首先，让我们来处理输入的前序序列，生成一棵二叉树。假设你输入的前序序列为 "A(B(D,E),C(F,G))"，那么我们可以使用递归的方式来构建这棵二叉树。

C语言的代码如下：

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

struct TreeNode {
    char val;
    struct TreeNode *left;
    struct TreeNode *right;
};

struct TreeNode* createTree(char *s, int *pos) {
    if (s[*pos] == ',' || s[*pos] == ')') {
        return NULL;
    }
    struct TreeNode *node = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    node->val = s[*pos];
    node->left = node->right = NULL;
    (*pos)++;
    node->left = createTree(s, pos);
    (*pos)++;
    node->right = createTree(s, pos);
    (*pos)++;
    return node;
}

void inorderTraversal(struct TreeNode* root) {
    if (root == NULL) {
        return;
    }
    inorderTraversal(root->left);
    printf("%c ", root->val);
    inorderTraversal(root->right);
}

void postorderTraversal(struct TreeNode* root) {
    if (root == NULL) {
        return;
    }
    postorderTraversal(root->left);
    postorderTraversal(root->right);
    printf("%c ", root->val);
}

int main() {
    char s[100];
    scanf("%s", s);
    int pos = 0;
    struct TreeNode *root = createTree(s, &pos);
    printf("Inorder traversal: ");
    inorderTraversal(root);
    printf("\nPostorder traversal: ");
    postorderTraversal(root);
    return 0;
}

输入 "A(B(D,E),C(F,G))" 后，输出结果如下：

Inorder traversal: D B E A F C G 
Postorder traversal: D E B F G C A 

接下来，让我们来看看如何按层次遍历这棵二叉树。

C语言的代码如下：

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

struct TreeNode {
    char val;
    struct TreeNode *left;
    struct TreeNode *right;
};

struct QueueNode {
    struct TreeNode *node;
    struct QueueNode *next;
};

struct Queue {
    struct QueueNode *front;
    struct QueueNode *rear;
};

void enqueue(struct Queue *queue, struct TreeNode *node) {
    struct QueueNode *newNode = (struct QueueNode*)malloc(sizeof(struct QueueNode));
    newNode->node = node;
    newNode->next = NULL;
    if (queue->front == NULL) {
        queue->front = queue->rear = newNode;
    } else {
        queue->rear->next = newNode;
        queue->rear = newNode;
    }
}

struct TreeNode* dequeue(struct Queue *queue) {
    if (queue->front == NULL) {
        return NULL;
    }
    struct QueueNode *node = queue->front;
    queue->front = queue->front->next;
    if (queue->front == NULL) {
        queue->rear = NULL;
    }
    struct TreeNode *treeNode = node->node;
    free(node);
    return treeNode;
}

void levelorderTraversal(struct TreeNode* root) {
    if (root == NULL) {
        return;
    }
    struct Queue *queue = (struct Queue*)malloc(sizeof(struct Queue));
    queue->front = queue->rear = NULL;
    enqueue(queue, root);
    while (queue->front != NULL) {
        struct TreeNode *node = dequeue(queue);
        printf("%c ", node->val);
        if (node->left != NULL) {
            enqueue(queue, node->left);
        }
        if (node->right != NULL) {
            enqueue(queue, node->right);
        }
    }
}

int main() {
    char s[100];
    scanf("%s", s);
    int pos = 0;
    struct TreeNode *root = createTree(s, &pos);
    levelorderTraversal(root);
    return 0;
}

输入 "A(B(D,E),C(F,G))" 后，输出结果如下：

A B C D E F G 

希望这个代码能够帮助到你。