if (!(T = (BiTNode *)malloc(sizeof(BiTNode)))) return ERROR;

This line of code is trying to allocate memory dynamically for a binary tree node using the function `malloc()`.

The `sizeof(BiTNode)` calculates the size of the `BiTNode` struct in bytes, which is then passed as an argument to `malloc()`.

The `if` statement checks if the memory allocation was successful - if `malloc()` returns a null pointer, then the condition is true (since `!(null)` is true), and the function will return an error.

If the memory allocation is successful, then the pointer to the newly allocated memory block is assigned to the variable `T`.

相关问题

#include <iostream> #include <string> #include <memory> using namespace std; struct BitNode { string data; BitNode* lchild; BitNode* rchild; }; void CreateBiTree(BitNode*& t) { string ch; cin >> ch; if (ch[0] == '#') { t = NULL; } else { t = new BitNode; t->data = ch; CreateBiTree(t->lchild); CreateBiTree(t->rchild); } } int InOrderTraverse(BitNode* t) { string op = t->data; int a, b; if (op[0] < '0' || op[0] > '9') { cout << '('; a = InOrderTraverse(t->lchild); cout << t->data; b = InOrderTraverse(t->rchild); cout << ')'; if (op == "+") return a + b; else if (op == "-") return a - b; else if (op == "*") return a * b; else return a / b; } else { cout << t->data; int num = 0; for (int i = 0; i < op.size(); i++) { num = num * 10 + op[i] - '0'; } return num; } } int main() { BitNode* tree = new BitNode; string ch; int sum; while (cin >> ch) { tree->data = ch; CreateBiTree(tree->lchild); CreateBiTree(tree->rchild); sum = InOrderTraverse(tree); printf("=%d\n", sum); } system("pause"); return 0; }用c实现

这段代码是用 C++ 实现的，如果要用 C 语言实现的话，需要对代码进行修改。

首先，需要将头文件修改为：

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

然后，需要将结构体的定义修改为：

struct BitNode {
    char data[10];
    struct BitNode* lchild;
    struct BitNode* rchild;
};

接着，需要修改 CreateBiTree 函数：

void CreateBiTree(struct BitNode** t) {
    char ch[10];
    scanf("%s", ch);
    if (ch[0] == '#') {
        *t = NULL;
    } else {
        *t = (struct BitNode*)malloc(sizeof(struct BitNode));
        strcpy((*t)->data, ch);
        CreateBiTree(&(*t)->lchild);
        CreateBiTree(&(*t)->rchild);
    }
}

最后，需要修改 InOrderTraverse 函数：

int InOrderTraverse(struct BitNode* t) {
    char* op = t->data;
    int a, b;
    if (op[0] < '0' || op[0] > '9') {
        printf("(");
        a = InOrderTraverse(t->lchild);
        printf("%s", t->data);
        b = InOrderTraverse(t->rchild);
        printf(")");
        if (strcmp(op, "+") == 0)
            return a + b;
        else if (strcmp(op, "-") == 0)
            return a - b;
        else if (strcmp(op, "*") == 0)
            return a * b;
        else
            return a / b;
    } else {
        printf("%s", t->data);
        int num = 0;
        for (int i = 0; i < strlen(op); i++) {
            num = num * 10 + op[i] - '0';
        }
        return num;
    }
}

完整的 C 语言代码如下：

#include <stdio.h> #include <stdlib.h> // 二叉树节点的结构体 typedef struct BiTNode { char data; struct BiTNode* lchild; struct BiTNode* rchild; } BiTNode; // 建立二叉树 BiTNode* createBiTNode(char* s, int* i) { char c = s[(*i)++]; if (c == '□') { return NULL; } BiTNode* root = ( BiTNode*)malloc(sizeof( BiTNode)); root->data = c; root->lchild = createBiTNode(s, i); root->rchild = createBiTNode(s, i); return root; } // 释放二叉树 void BiTNode( BiTNode* root) { if (root) { destroyBinaryTree(root->lchild); destroyBinaryTree(root->rchild); free(root); } } // 先序遍历 void preorderTraversal( BiTNode* root) { if (root) { printf("%c ", root->data); preorderTraversal(root->lchild); preorderTraversal(root->rchild); } } // 中序遍历 void inorderTraversal( BiTNode* root) { if (root) { inorderTraversal(root->lchild); printf("%c ", root->val); inorderTraversal(root->rchild); } } // 后序遍历 void postorderTraversal( BiTNode* root) { if (root) { postorderTraversal(root->lchild); postorderTraversal(root->rchild); printf("%c ", root->val); } } int main() { char s[] = "AB□C□□D□□"; int i = 0; BiTNode* root = createBiTNode(s, &i); printf("中序遍历结果："); inorderTraversal(root); printf("\n"); destroyBiTNode(root); return 0; }找出以上程序错误并修改

在程序中，释放二叉树的函数名应该为 destroyBinaryTree 而不是 BiTNode，因为这个函数名与定义结构体时的名字冲突了。同时，在中序遍历和后序遍历函数中，输出节点数据时应该使用 root->data 而不是 root->val。修改后的程序如下：

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

typedef struct BiTNode {     
    char data;     
    struct BiTNode* lchild;     
    struct BiTNode* rchild; 
} BiTNode;  

BiTNode* createBiTNode(char* s, int* i) {     
    char c = s[(*i)++];     
    if (c == '□') {         
        return NULL;     
    }      
    BiTNode* root = (BiTNode*)malloc(sizeof(BiTNode));     
    root->data = c;     
    root->lchild = createBiTNode(s, i);     
    root->rchild = createBiTNode(s, i);     
    return root; 
}  

void destroyBinaryTree(BiTNode* root) {     
    if (root) {         
        destroyBinaryTree(root->lchild);         
        destroyBinaryTree(root->rchild);         
        free(root);     
    } 
}  

void preorderTraversal(BiTNode* root) {     
    if (root) {         
        printf("%c ", root->data);         
        preorderTraversal(root->lchild);         
        preorderTraversal(root->rchild);     
    } 
}  

void inorderTraversal(BiTNode* root) {     
    if (root) {         
        inorderTraversal(root->lchild);         
        printf("%c ", root->data);         
        inorderTraversal(root->rchild);     
    } 
}  

void postorderTraversal(BiTNode* root) {     
    if (root) {         
        postorderTraversal(root->lchild);         
        postorderTraversal(root->rchild);         
        printf("%c ", root->data);     
    } 
}  

int main() {     
    char s[] = "AB□C□□D□□";     
    int i = 0;      
    BiTNode* root = createBiTNode(s, &i);     
    printf("中序遍历结果：");     
    inorderTraversal(root);     
    printf("\n");     
    destroyBinaryTree(root);     
    return 0; 
}