c++ - 如何在 C++ 中查看哈希项？

Question

您好，我有以下代码，我希望能够向其中插入单词，并能够通过打印出来查看我放入散列中的内容。这是我拥有的:

#include <iostream>
#include <fstream>
#include <string>
#include <hash_map>
#include <set>
#include <windows.h>

using namespace std;

struct nlist{
    struct nlist *next;
    char *name;
    char *defn;
};

#define HASHSIZE 101

static struct nlist *hashtab[HASHSIZE];

unsigned hash(const char *s)
{
    unsigned hashval;

    for (hashval = 0; *s != '\0'; s++)
        hashval = *s + 31 * hashval;
    return hashval % HASHSIZE;
}

struct nlist *lookup(const char *s)
{
    struct nlist *np;

    for (np = hashtab[hash(s)]; np != NULL; np = np->next)
        if (strcmp(s,np -> name) == 0)
            return np;
    return NULL;
}

struct nlist *install(const char *name, const char *defn)
{
    struct nlist *np;
    unsigned hashval;

    if ((np = lookup(name)) == NULL){
        np = (struct nlist *) malloc (sizeof(*np));
        if (np == NULL || (np -> name = strdup(name)) == NULL)
            return NULL;
        hashval = hash(name);
        np->next = hashtab[hashval];
        hashtab[hashval] = np;
    }
    else{
        free((void *) np->defn);

    }
    if ((np -> defn = strdup(defn)) == NULL)
        return NULL;
    return np;
}

int main(){

    cout << "yo";
    string inline1;
    while (1){
        getline(cin, inline1);
        if (inline1 == "hash"){
            getline(cin, inline1);
            cout << hash(inline1.c_str()) << '\n';
        }
        else if (inline1 == "lookup"){
            getline(cin, inline1);
            cout << lookup(inline1.c_str()) << '\n';
        }
        else if (inline1 == "install"){
            getline(cin, inline1);
            string inline2;
            getline(cin, inline2);
            cout << install(inline1.c_str(), inline2.c_str()) << '\n';
        }
    }
}

Answer 1

您在这里遇到的问题是，您正在打印指向您已查找的 nlist 项目的指针，而不是其中的 defn 字符串的值那个项目。

在您的主循环中，您有以下代码:

else if (inline1 == "lookup"){
        getline(cin, inline1);
        cout << lookup(inline1.c_str()) << '\n';
}

您可能想要的是:

else if (inline1 == "lookup"){
        getline(cin, inline1);
        cout << lookup(inline1.c_str())->defn << '\n';
}