给出一棵二叉树的中序遍历和前序遍历，求它的后序遍历，请给出完整c语言代码

下面是给出的二叉树结构体定义和求解后序遍历的完整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) {
    int i;
    for (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 || inorderSize <= 0) {
        return NULL;
    }
    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
    root->val = preorder[0];
    int rootIndex = search(inorder, 0, inorderSize - 1, root->val);
    root->left = buildTree(preorder + 1, rootIndex, inorder, rootIndex);
    root->right = buildTree(preorder + rootIndex + 1, preorderSize - rootIndex - 1, inorder + rootIndex + 1, inorderSize - rootIndex - 1);
    return root;
}

void postorderTraversal(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};
    int inorder[] = {4, 2, 5, 1, 3, 6};
    int size = sizeof(preorder) / sizeof(int);
    TreeNode* root = buildTree(preorder, size, inorder, size);
    printf("The postorder traversal of the binary tree is: ");
    postorderTraversal(root);
    printf("\n");
    return 0;
}

上述代码中，search函数用于在中序遍历数组中找到根节点的位置；buildTree函数用于递归构建二叉树；postorderTraversal函数用于递归遍历二叉树并输出后序遍历结果。在主函数中，我们给出了一个示例，构建了一棵二叉树，并输出了它的后序遍历结果。