使用C++实现kmp算法

以下是使用C语言实现KMP算法的示例代码：

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

void getNext(char* pattern, int* next) {
    int i = 0, j = -1;
    next[0] = -1;
    int len = strlen(pattern);
    while (i < len - 1) {
        if (j == -1 || pattern[i] == pattern[j]) {
            ++i;
            ++j;
            if (pattern[i] != pattern[j]) {
                next[i] = j;
            } else {
                next[i] = next[j];
            }
        } else {
            j = next[j];
        }
    }
}

int kmp(char* text, char* pattern) {
    int len1 = strlen(text);
    int len2 = strlen(pattern);
    int* next = (int*)malloc(len2 * sizeof(int));
    getNext(pattern, next);
    int i = 0, j = 0;
    while (i < len1 && j < len2) {
        if (j == -1 || text[i] == pattern[j]) {
            ++i;
            ++j;
        } else {
            j = next[j];
        }
    }
    free(next);
    if (j == len2) {
        return i - j;
    } else {
        return -1;
    }
}

int main() {
    char text[100], pattern[100];
    printf("Enter the text string: ");
    scanf("%s", text);
    printf("Enter the pattern string: ");
    scanf("%s", pattern);
    int pos = kmp(text, pattern);
    if (pos == -1) {
        printf("The pattern string is not found in the text string.\n");
    } else {
        printf("The pattern string is found in the text string at position %d.\n", pos);
    }
    return 0;
}

在上述代码中，getNext函数用于计算模式串的next数组，kmp函数用于在文本串中查找模式串。该代码使用了动态内存分配来分配next数组，使用了字符串库中的strlen函数来计算字符串的长度。