上下文无关文法的存储与产生式的查找

Question

似乎没有把数据存储进去，不知道为什么，请看看

#include<iostream>
using namespace std;
const int MaxVnNum = 20;
const int MaxVtNum = 20;
const int Max = 20;

struct Vt {
    int num;
    char right[Max];
    struct Vt *next;
};
struct Vn {
    char vn;
    struct Vt vt;
};
struct Vn grammar[MaxVnNum];
//创建表头，即创建结构体变量
struct Vt* createHead()
{
    //1.动态内存申请
    struct Vt* headNode = (struct Vt*)malloc(sizeof(struct Vt));
    //(*headNode).next = NULL;
    headNode->next = NULL;//变量要初始化
    return headNode;   //返回变量
}

struct Vt* createNode(int data,string exper)
{
    struct Vt* newNode = (struct Vt*)malloc(sizeof(struct Vt));
    newNode->num = data;
    for (int m = 0; m < exper.length(); m++)
    {
        newNode->right[Max] = exper[m];
    }
    newNode->next = NULL;  //作为链表结束标志
    return newNode;
}
//表尾插入
void insertByTail(struct Vt* headNode, int data,string exper)
{
    struct Vt* newNode = createNode(data,exper);
    struct Vt* pTail = headNode;
    while (pTail->next != NULL)
    {
        pTail = pTail->next;
    }
    pTail->next = newNode;
}
//查找链表
void printList(struct Vt* headNode,char L,int x)
{
    //为什么指向第二个节点？ 因为第一个节点没有存数据
    struct Vt* pMove = headNode->next;
    while (pMove->num != x&&pMove->next!=NULL)
    {
        pMove = pMove->next;
    }
    if (pMove->next != NULL)
    {
        cout << L << "->"<<pMove->right ;
        
    }
    printf("\n");
}

void enter(int n, Vt* list)
{
    //struct Vn grammar[MaxVnNum];
    int rcount = 0;
    char left;
    for (int i = 0; i < n; i++)
    {
        string exper;
        cout << "输入左部：" ;
        cin >> left;
        grammar[i].vn = left;
        
        cout << "输入右部文法个数：" ;
        cin >> rcount;
        for (int j = 0; j < rcount; j++)
        {
            cout << "输入第"<<j+1<<"个表达式:";
            cin >> exper;
            if (j == 0)
            {
                createNode(j + 1, exper);
            }
            else {
                insertByTail(list, j + 1, exper);
            }


        }


    }
}
void search(struct Vt* list,char L,int n)
{
    int x;
    bool a = false;
    for (int i = 0; i < n; i++)
    {
        if (L == grammar[i].vn)
        {
            cout << "找到对应非终结符" << endl;
            cout << "输入查找的第几个式子：";
            cin >> x;
            printList(list, L, x);
            
        }
    }
    if (!a)
    {
        cout << "没有找到对应的产生式";
    }
}
int main()
{
    struct Vt* list = createHead();
    //输入产生式个数
    cout << "输入产生式个数"<<endl;
    int n;
    cin >> n;
    //输入产生式，进行存储
    enter(n, list);
    //输入要寻找的产生式
    char w;
    cout << "输入要寻找的非终结符的产生式" << endl;
    cin >> w;
    search(list,w,n);
}

Answer 1

• 这个问题的回答你可以参考下: https://ask.csdn.net/questions/7638558
• 这篇博客你也可以参考下：编译原理实验一（上下文无关文法的表示与存储）
• 这篇博客也不错, 你可以看下编译原理实验一（上下文无关文法的表示与存储）