请用c++帮我实现KMP算法

以下是C++实现的KMP算法代码：

#include <iostream>
#include <cstring>

using namespace std;

// 计算next数组
void getNext(char* p, int* next, int len) {
    int i = 0, j = -1;
    next[0] = -1;
    while (i < len) {
        if (j == -1 || p[i] == p[j]) {
            i++;
            j++;
            next[i] = j;
        } else {
            j = next[j];
        }
    }
}

// KMP算法
int kmp(char* s, char* p) {
    int slen = strlen(s);
    int plen = strlen(p);
    int* next = new int[plen];
    getNext(p, next, plen);
    int i = 0, j = 0;
    while (i < slen && j < plen) {
        if (j == -1 || s[i] == p[j]) {
            i++;
            j++;
        } else {
            j = next[j];
        }
    }
    delete[] next;
    if (j == plen) {
        return i - j;
    } else {
        return -1;
    }
}

int main() {
    char s[] = "hello world";
    char p[] = "world";
    int pos = kmp(s, p);
    if (pos == -1) {
        cout << "not found" << endl;
    } else {
        cout << "found at position " << pos << endl;
    }
    return 0;
}