已知一个二叉树，由前序遍历和后序遍历构建二叉树的C语言代码

以下是由前序遍历和后序遍历构建二叉树的C语言代码：

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

typedef struct TreeNode {
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
} TreeNode;

int search(int* arr, int start, int end, int value) {
    for (int i = start; i <= end; i++) {
        if (arr[i] == value) {
            return i;
        }
    }
    return -1;
}

TreeNode* buildTree(int* preorder, int preorderSize, int* inorder, int inorderSize) {
    if (preorderSize == 0) {
        return NULL;
    }

    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
    root->val = preorder[0];

    if (preorderSize == 1) {
        root->left = NULL;
        root->right = NULL;
        return root;
    }

    int index = search(inorder, 0, inorderSize - 1, preorder[0]);
    int leftSize = index;
    int rightSize = inorderSize - index - 1;

    root->left = buildTree(preorder + 1, leftSize, inorder, leftSize);
    root->right = buildTree(preorder + leftSize + 1, rightSize, inorder + index + 1, rightSize);

    return root;
}

void postorder(TreeNode* root) {
    if (root == NULL) {
        return;
    }

    postorder(root->left);
    postorder(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 size = sizeof(preorder) / sizeof(preorder[0]);

    TreeNode* root = buildTree(preorder, size, inorder, size);

    printf("The postorder traversal of the constructed binary tree is: ");
    postorder(root);

    return 0;
}

这个代码会构建一个二叉树，然后输出后序遍历的结果。你可以将前序遍历和后序遍历的数组改成你需要的输入。