c语言实现二叉树先序中序后序遍历

以下是C语言实现二叉树先序、中序、后序遍历的示例代码：

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

// 二叉树结构体
struct TreeNode {
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
};

// 创建新节点
struct TreeNode* createNode(int val) {
    struct TreeNode* node = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    node->val = val;
    node->left = NULL;
    node->right = NULL;
    return node;
}

// 构建二叉树
struct TreeNode* buildTree(int* preorder, int preStart, int preEnd, int* inorder, int inStart, int inEnd) {
    if (preStart > preEnd || inStart > inEnd) {
        return NULL;
    }
    struct TreeNode* root = createNode(preorder[preStart]);
    int rootIndex = inStart;
    while (rootIndex <= inEnd && inorder[rootIndex] != preorder[preStart]) {
        rootIndex++;
    }
    int leftSize = rootIndex - inStart;
    root->left = buildTree(preorder, preStart + 1, preStart + leftSize, inorder, inStart, rootIndex - 1);
    root->right = buildTree(preorder, preStart + leftSize + 1, preEnd, inorder, rootIndex + 1, inEnd);
    return root;
}

// 先序遍历
void preorderTraversal(struct TreeNode* root) {
    if (root == NULL) {
        return;
    }
    printf("%d ", root->val);
    preorderTraversal(root->left);
    preorderTraversal(root->right);
}

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

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

int main() {
    int preorder[] = {1, 2, 4, 5, 3, 6, 7};
    int inorder[] = {4, 2, 5, 1, 6, 3, 7};
    int n = sizeof(preorder) / sizeof(preorder[0]);
    struct TreeNode* root = buildTree(preorder, 0, n - 1, inorder, 0, n - 1);
    printf("先序遍历: ");
    preorderTraversal(root);
    printf("\n中序遍历: ");
    inorderTraversal(root);
    printf("\n后序遍历: ");
    postorderTraversal(root);
    printf("\n");
    return 0;
}

这段代码中，`buildTree` 函数用于构建二叉树，`preorderTraversal` 函数用于先序遍历二叉树，`inorderTraversal` 函数用于中序遍历二叉树，`postorderTraversal` 函数用于后序遍历二叉树。在 `main` 函数中，先构建二叉树，然后分别进行先序、中序、后序遍历并输出结果。