串的模式匹配

#define _CRT_SUCURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#define N 255

int Index_BF(char original[], char object[]);//Brute-Force返回值为0表示匹配失败
int Index_KMP(char original[], char object[]);
int* Get_Next(char object[]);
int* Get_Nextval(char object[]);

int main(void)
{
    int pos;//模式串在主串的位置
    char original[N];
    char object[N];

    printf("请输入主串\n");
    gets_s(original);
    printf("请输入模式串\n");
    gets_s(object);

    if (0 == (pos = Index_BF(original, object)))
    {
        printf("\n匹配失败\n");
        exit(-1);
    }
    printf("(BF)模式串在主串的位置是:%d\n", pos);

    if ( 0 == (pos = Index_KMP(original, object)))
    {
        printf("\n匹配失败\n");
        exit(-1);
    }
    printf("(KMP_nextval)模式串在主串的位置是:%d\n", pos);

    system("pause");
    return 0;
}

int Index_BF(char original[], char object[])
{
    int i = 0;
    int j = 0;
    int original_len = 0;
    int object_len = 0;

    while (original[++original_len] != '\0');
    while (object[++object_len] != '\0');

    if (original_len == 0 ||object_len == 0 || original_len < object_len)
    {
        printf("\n模式匹配参数不合法\n!");
        return 0;
    }

    while (i < original_len && j < object_len)
    {
        if (original[i] == object[j])
        {
            i++;
            j++;
        }
        else
        {
            i = i - j + 1;//主串回溯到 i - j + 1 的位置重新比较
            j = 0;//模式串重头开始比较
        }
    }
    if (j > object_len - 1)
    {
        return i - object_len + 1;
    }
    else
    {
        return 0;
    }
}

int Index_KMP(char original[], char object[])
{
    int i = 0;
    int j = 0;
    int original_len = 0;
    int object_len = 0;
    int* next = Get_Next(object);
    int* nextval = Get_Nextval(object);
    while (original[++original_len] != '\0');//获得串长
    while (object[++object_len] != '\0');

    if (original_len < 0 || object_len < 0 || original_len < object_len)
    {
        printf("\n模式匹配参数不合法\n!");
        return 0;
    }

    while (i < original_len && j < object_len)
    {
        if (j == -1 || original[i] == object[j])//当 j == - 1时，进入循环加1。以保证 j 指向匹配串下标0的元素
        {
            ++i;
            ++j;
        }
        else
        {
            j = nextval[j];
        }
    }

    if (j > (object_len - 1))
    {
        return i - object_len + 1;
    }
    else
    {
        return 0;
    }
}

int* Get_Next(char object[])
{
    int k = -1;
    int j = 0;
    int object_len = 0;
    while (object[++object_len] != '\0');
    int* next = (int*)calloc(object_len, sizeof(int));

    next[0] = -1;
    while (j < object_len)
    {
        if (k == -1 || object[j] == object[k])
        {
            next[++j] = ++k;
        }
        else
        {
            k = next[k];
        }
    }
    return next;
}

int* Get_Nextval(char object[])
{
    int j = 1;
    int k = 0;
    int object_len = 0;
    int* next = Get_Next(object);
    while ((object[++object_len]) != '\0');
    int* nextval = (int*)calloc(object_len, sizeof(int));

    nextval[0] = -1;
    while (j < object_len)
    {
        k = next[j];//k 是 模式串中第 j 个元素的最大滑动距离
        if (object[j] == object[k])//模式串第  j 个元素和第 j - 1 个元素相同时
        {
            nextval[j] = nextval[k];//当模式串中第 j 个元素与主串对应元素失配，则第 j - 1 个元素也失配
        }
        else
        {
            nextval[j] = next[j];//模式串第  j 个元素和第 j - 1 个元素失配时
        }
        j++;
    }
    return nextval;
}