C言語で文字列分割(4次元配列をつかって)

#内容
hackerrankの問題から
document→paragraph(改行区切り)→sentence(ピリオド区切り)→word(スペース区切り)

メモ用なので、関数化前＆コメントなし
もうちょっと練ってから書き始めればよかった。
似たような操作しかないので、しっかり練ったら芸術的なプログラムになりそう

#コード

split.c

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

char**** get_document(char* text) {
    char**** result;
    //result = malloc(sizeof(char)*strlen(text));
    //char* buf = malloc(sizeof(char)*strlen(text));
    char** split_para = malloc(sizeof(char*)*5);
    int index_para=0;
    char* ptr;
    ptr = strtok(text,"\n");
    while(ptr != NULL){
        split_para[index_para] = malloc(sizeof(char)*strlen(ptr));
        strcpy(split_para[index_para],ptr);
        index_para++;
        ptr = strtok(NULL,"\n");
    }
    char*** split_sentence = malloc(sizeof(char**)*index_para);
    int index_sentence = 0;
    for(int i=0;i<index_para;i++){
        index_sentence = 0;
        ptr = strtok(split_para[i],".");
        while(ptr != NULL){
            split_sentence[i] = realloc(split_sentence[i],sizeof(char*)*(index_sentence+1));
            split_sentence[i][index_sentence] = malloc(sizeof(char)*strlen(ptr));
            strcpy(split_sentence[i][index_sentence],ptr);
            index_sentence++;
            ptr = strtok(NULL,".");
        }
    }
    free(split_para);
    char**** split_word = malloc(sizeof(char***)*index_para);
    int index_word = 0;
    for(int i=0;i<index_para;i++){
        index_sentence = 0;
        while(split_sentence[i][index_sentence] != NULL){
            split_word[i] = realloc(split_word[i],sizeof(char**)*(index_sentence+1));
            index_word = 0;
            ptr = strtok(split_sentence[i][index_sentence]," ");
            while(ptr != NULL){
                split_word[i][index_sentence] = realloc(split_word[i][index_sentence],sizeof(char*)*(index_word+1));
                split_word[i][index_sentence][index_word] = malloc(sizeof(char)*strlen(ptr));
                strcpy(split_word[i][index_sentence][index_word],ptr);
                index_word++;
                ptr = strtok(NULL," ");
            }
            index_sentence++;
        }
    }
    free(split_sentence);
    result = split_word;

    return result;
}