内存错误（sysmalloc:assertion),求大神指点

class Solution {
public:
int strStr(string haystack, string needle) {
int hay_len = haystack.length();
int needle_len = needle.length();
int i = 0, j = 0;
int* next = new int[needle_len];
getNext(needle, next);
while(i < hay_len && j < needle_len){
if(j == -1 || haystack[i] == needle[j]){
++i;
++j;
}
else{
j = next[j];
}
}
if(j >= needle_len)
return i - j;
else
return -1;

}

public:
void getNext(string needle, int next[]){
int n = needle.length();
int j = -1;
int i = 0
next[0] = -1;
while(i < n) {
if (j == -1 || needle[i] == needle[j]) {
++i;
++j;
next[i] = j;
}
else
j = next[j];
}
}
};

 # include <iostream>
# include <cstring>
# include <algorithm>
using namespace std;

int next_[100];

void get_next(char *T)
{
    int i = 1;
    int j = 0;
    next_[1] = 0;
    int len = strlen(T);

    while (i < len)
    {
        if (j == 0 || T[i] == T[j])
        {
            ++i;
            ++j;
            next_[i] = j;
        }
        else
        {
            j = next_[j];
        }
    }
    for (i = 0; i < len; i++)
    {
        cout << next_[i] << " ";
    }
    cout << endl;
}

bool KMP(char *S, char *T)
{
    cout << "begin" << endl;
    int i = 1;
    int j = 1;
    int len_s = strlen(S);
    int len_t = strlen(T);
    while (i < len_s && j < len_t)
    {
        if (j == 0 || S[i] == T[j])
        {
            ++i;
            ++j;
        }
        else
        {
            j = next_[j];
        }
    }
    cout << j << endl;
    if (j >= len_t)
    {
        cout << "hello" << endl;
        return true;
    }
    else
        return false;
}

int main()
{
    char S[100] = "0aaaaaaabcdefa";
    char T[100] = "0aaaabcd";
    next_[0] = 1;
    memset(next_, 0, sizeof(next_));
    get_next(T);
    bool k = KMP(S, T);
    cout << k << endl;
}