已知一个二叉树的前序遍历序列和中序遍历序列，求其后序遍历序列。c语言

代码实现如下：

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

typedef struct TreeNode{
    int val;  // 节点值
    struct TreeNode* left;  // 左子节点
    struct TreeNode* right;  // 右子节点
}TreeNode;

TreeNode* buildTree(int* preorder, int* inorder, int preorderStart, int preorderEnd, int inorderStart, int inorderEnd);
void postorderTraversal(TreeNode* root);

int main(){
    int preorder[] = {1, 2, 4, 5, 3, 6, 7}; // 前序遍历序列
    int inorder[] = {4, 2, 5, 1, 6, 3, 7};  // 中序遍历序列
    int n = sizeof(preorder) / sizeof(int);  // 序列长度

    TreeNode* root = buildTree(preorder, inorder, 0, n - 1, 0, n - 1); // 构建二叉树

    printf("后序遍历序列为：");
    postorderTraversal(root);  // 后序遍历输出

    return 0;
}

// 根据前序遍历序列和中序遍历序列构建二叉树
TreeNode* buildTree(int* preorder, int* inorder, int preorderStart, int preorderEnd, int inorderStart, int inorderEnd){
    if(preorderStart > preorderEnd){
        return NULL;
    }

    int rootVal = preorder[preorderStart];
    int index = inorderStart;
    while(inorder[index] != rootVal){
        index++;
    }

    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
    root->val = rootVal;
    root->left = buildTree(preorder, inorder, preorderStart + 1, preorderStart + index - inorderStart, inorderStart, index - 1);
    root->right = buildTree(preorder, inorder, preorderStart + index - inorderStart + 1, preorderEnd, index + 1, inorderEnd);
    return root;
}

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