linux c언어 coredumped 에러입니다 ㅠ 프로그래밍 괴수님들 부탁드립니다

#include <stdio.h>
#include <string.h>
 
typedef struct tokfq freq;
struct tokfq{
        char *token;
        int frequency;
};
void frequency(char *tokens[],freq fq[]){
        int i=0,j=0,n=0;
        while (tokens[i]!=NULL){
                for(j=0;j<n;j++){
                        if (strcmp(tokens[i],fq[j].token)==0){
                                fq[j].frequency++;
                                break;
                        }
                }
                if(j>=n){
                        fq[n].token=tokens[i];
                        fq[n].frequency=1;
                        n++;
                }
                i++;
        }
        printf("Frequencies: ");
        for (i=0;i<n;i++){
                printf("%s %d ", fq[i].token, fq[i].frequency);
        }
 
}
void tokenize(char buf[],char *tokens[]){
        tokens[0]=strtok(buf," ");
        int i=0, j;
        for(;;){
                i++;
                tokens[i]=strtok(NULL," ");
                if(tokens[i]==NULL)break;
        }
        printf("There were %d words:",i);
        for(j=0;j<i;j++){
                printf("%s ",tokens[j]);
        }
        printf("\n");
}
void max_fq(freq fq[]){
        int i=0, max_n=0;
        int fmax=fq[0].frequency;
        while (fq[i].frequency>0){
                if(fq[i].frequency>fmax){
                        fmax=fq[i].frequency;
                        max_n=i;
                }
                i++;
}
        printf("\nThe word with the max freq:%s\n",fq[max_n].token);
}
void read(char buf[]){
        printf("Enter a sentence\n");
        fgets(buf,50,stdin);
        buf[strlen(buf)-1]=0;
        printf("You entered %s\n",buf);
}
 
void main(){
        char buf[50];
        char *tokens[50];
        freq fq[30];
 
        read(buf);
        tokenize(buf,tokens);
        frequency(tokens,fq);
        max_fq(fq);
}
 
헉 죄송합니다 ㅠㅠ