kmp算法next计算方法C语言,KMP(next)算法c语言实现

KMP算法中的next数组计算方法如下：

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

KMP算法的C语言实现如下：

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

void getNext(char *p, int *next);
int kmp(char *s, char *p);

int main() {
    char s[100], p[100];
    printf("请输入主串：");
    scanf("%s", s);
    printf("请输入模式串：");
    scanf("%s", p);
    int pos = kmp(s, p);
    if (pos == -1) {
        printf("未找到匹配的子串\n");
    } else {
        printf("匹配的子串起始位置为：%d\n", pos);
    }
    return 0;
}

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

int kmp(char *s, char *p) {
    int sLen = strlen(s);
    int pLen = strlen(p);
    int next[pLen];
    getNext(p, next);
    int i = 0, j = 0;
    while (i < sLen && j < pLen) {
        if (j == -1 || s[i] == p[j]) {
            ++i;
            ++j;
        } else {
            j = next[j];
        }
    }
    if (j == pLen) {
        return i - j;
    } else {
        return -1;
    }
}