kmp算法用c代码实现

以下是KMP算法的C语言实现：

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

void computeLPSArray(char* pat, int M, int* lps); //计算lps数组的函数

void KMPSearch(char* pat, char* txt)
{
    int M = strlen(pat);
    int N = strlen(txt);

    int lps[M];

    computeLPSArray(pat, M, lps); //计算lps数组

    int i = 0;  //txt中的指针
    int j = 0;  //pat中的指针
    while (i < N) {
        if (pat[j] == txt[i]) {
            j++;
            i++;
        }
        if (j == M) {
            printf("Found pattern at index %d\n", i - j);
            j = lps[j - 1];
        }

        else if (i < N && pat[j] != txt[i]) {
            if (j != 0)
                j = lps[j - 1];
            else
                i++;
        }
    }
}

void computeLPSArray(char* pat, int M, int* lps)
{
    int len = 0;
    int i = 1;
    lps[0] = 0; //lps[0] 总是0

    while (i < M) {
        if (pat[i] == pat[len]) {
            len++;
            lps[i] = len;
            i++;
        }
        else {
            if (len != 0) {
                len = lps[len - 1];
            }
            else {
                lps[i] = 0;
                i++;
            }
        }
    }
}

int main()
{
    char txt[] = "ABABDABACDABABCABAB";
    char pat[] = "ABABCABAB";
    KMPSearch(pat, txt);
    return 0;
}

输出结果为：

Found pattern at index 10