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最新推荐文章于 2025-12-22 09:47:08 发布

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#哈希算法 #算法

文章介绍了如何使用C语言实现哈希表，包括创建、插入和查找功能，以及在给定数组中使用二分查找算法查找特定键值。

1.请编程实现哈希表的创建存储数组{12,24,234,234,23,234,23},输入key查找的值,实现查找功能

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

typedef int datatype;
typedef struct Node
{
    datatype data;
    struct Node* next;
} *node;

node create_node()
{
    node p = (node)malloc(sizeof(struct Node));

    if (NULL == p)
    {
        return NULL;
    }

    p->data = 0;
    p->next = NULL;
    return p;
}

int prime(int m)
{
    for (int i = m; i >= 2; i--)
    {
        int flag = 0;

        for (int j = 2; i <= sqrt(i); j++)
        {
            if (i % j == 0)
            {
                flag = -1;
                break;
            }
        }

        if (0 == flag)
        {
            return i;
        }
    }
}

void insert_hash(node hash[], datatype key, int p)
{
    int index = key % p;

    node s = create_node();
    s->data = key;
    if (NULL == hash[index])
    {
        hash[index] = s;
    }
    else
    {
        s->next = hash[index];
        hash[index] = s;
    }
}

int search_hash(node hash[], datatype key, int p)
{
    int index = key % p;
    node head = hash[index];
    while (head)
    {
        if (key == head->data)
        {
            return 0;
        }
        head = head->next;
    }

    return -1;
}

void show(node hash[], int m)
{
    for (int i = 0; i < m; i++)
    {
        printf("%d:", i);

        node p = hash[i];
        while (p)
        {
            printf("%-5d", p->data);
            p = p->next;
        }
        puts("NULL");
    }
}

int main()
{
    int a[] = {12, 24, 234, 234, 23, 234, 23};
    int len = sizeof(a) / sizeof(a[0]);
    int m = len * 4 / 3;

    node hash[m];
    for (int i = 0; i < m; i++)
    {
        hash[i] = NULL;
    }

    int p = prime(m);
    for (int i = 0; i < len; i++)
    {
        insert_hash(hash, a[i], p);
    }

    show(hash, m);

    datatype key;
    printf("输入 key:");
    scanf("%d", &key);
    int flag = search_hash(hash, key, p);
    if (0 == flag)
    {
        puts("存在");
    }
    else
    {
        puts("不存在");
    }

    return 0;
}

2.现有数组{12,23,45,56,445,5676,6888},请输入key实现二分查找

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


int half(int a[], int len, int key)
{
    int low = 0, high = len - 1;
    while (low <= high)
    {
        int mid = (low + high) / 2;
        if (a[mid] < key)
        {
            low = mid + 1;
        }
        else if (a[mid] > key)
        {
            high = mid - 1;
        }
        else
        {
            return mid;
        }
    }

    return -1;
}

int main()
{
    int a[] = {12, 23, 45, 56, 445, 5676, 6888};
    int len = sizeof(a) / sizeof(a[0]);
    for (int i = 0; i < len; i++)
    {
        printf("%5d", a[i]);
    }
    puts("");

    int key;
    printf("请输入 key:");
    scanf("%d", &key);

    int index = half(a, len, key);
    if (-1 == index)
    {
        printf("%d 不存在\n", key);
    }
    else
    {
        printf("%d 存在于 %d 位\n", key, index);
    }

    return 0;
}