c - 如何在 C（使用我正在使用的 DS）中为此 MergeSort 实现正确分配 memory？

/////// DICTIONARY METHODS //////// typedef struct { char *item; int weight; } item; typedef struct { item **wordlist; //track size of dictionary int size; } dict; //dict constructor dict* Dict(int count){ //allocate space for dictionary dict* D = malloc(sizeof(dict)); //allocate space for words D->wordlist = malloc(sizeof(item*) * count); //initial size D->size = 0; return D; } //word constructor item* Item(char str[]){ //allocate memory for struct item* W = malloc(sizeof(item)); //allocate memory for string W->item = malloc(sizeof(char) * strlen(str)); W->weight = 0; return W; } void merge(dict* D, int start, int middle, int stop){ //create ints to track lengths of left and right of array int leftlen = middle - start + 1; int rightlen = stop - middle; //create new temporary dicts to store the two sides of the array dict* L = Dict(leftlen); dict* R = Dict(rightlen); int i, j, k; //copy elements start through middle into left dict- this gives a segfault for (int i = 0; i < leftlen; i++){ L->wordlist[i] = malloc(sizeof(item*)); L->wordlist[i] = D->wordlist[start + i]; } //copy elements middle through end into right dict- this gives a segfault for (int j = 0; j < rightlen; j++){ R->wordlist[j] = malloc(sizeof(item*)); R->wordlist[j]= D->wordlist[middle + 1 + k]; } i = 0; j = 0; k = leftlen; while ((i < leftlen) && (j < rightlen)){ if (strcmp(L->wordlist[i]->item, R->wordlist[j]->item) <= 0) { D->wordlist[k] = L->wordlist[i]; i++; k++; } else{ D->wordlist[k] = R->wordlist[j]; j++; k++; } } while (i < leftlen){ D->wordlist[k] = L->wordlist[i]; i++; k++; } while (j < rightlen){ D->wordlist[k] = L->wordlist[j]; j++; k++; } } void mergeSort(dict* D, int start, int stop){ if (start < stop) { int middle = start + (stop - start) / 2; mergeSort(D, start, middle); mergeSort(D, middle + 1, stop); merge(D, start, middle, stop); }

#include <stdlib.h> #include <string.h> // Weighted Word -------------------------------------------------------------- // typedef struct { char *word; int weight; } weighted_word; // Create a weighted word // weighted_word* CreateWeightedWord(const char *str, int weight){ weighted_word* W = malloc(sizeof(weighted_word)); if (W){ W->word = malloc(strlen(str) + 1); // string length + nul terminator if (W->word) strcpy( W->word, str); W->weight = weight; } return W; } // Free a weighted word // weighted_word *FreeWeightedWord(weighted_word *W){ if (W){ if (W->word) free(W->word); free(W); } return NULL; } // Dictionary (of Weighted Words) --------------------------------------------- // typedef struct { weighted_word **wordlist; // this is a pointer to an array of (weighted_word *)s int size; // current number of elements in use int capacity; // maximum number of elements available to use } dict; // Create a dictionary with a fixed capacity // dict* CreateDict(int capacity){ dict* D = malloc(sizeof(dict)); if (D){ D->wordlist = malloc(sizeof(weighted_word*) * capacity); D->size = 0; D->capacity = capacity; } return D; } // Free a dictionary (and all weighted words) // dict *FreeDict(dict *D){ if (D){ for (int n = 0; n < D->size; n++) FreeWeightedWord(D->wordlist[n]); free(D->wordlist); free(D); } return NULL; } // Add a new weighted word to the end of our dictionary // void DictAddWord(dict *D, const char *str, int weight){ if (!D) return; if (D->size == D->capacity) return; D->wordlist[D->size] = CreateWeightedWord(str, weight); if (D->wordlist[D->size]) D->size += 1; } // Merge Sort the Dictionary -------------------------------------------------- // Merge two partitions of sorted words // words • the partitioned weighted word list // start • beginning of left partition // middle • end of left partition, beginning of right partition // stop • end of right partition // buffer • temporary work buffer, at least as big as (middle-start) // void MergeWeightedWords(weighted_word **words, int start, int middle, int stop, weighted_word **buffer){ int Lstart = start; int Rstart = middle; // Left partition int Lstop = middle; int Rstop = stop; // Right partition int Bindex = 0; // temporary work buffer output index // while (left partition has elements) AND (right partition has elements) while ((Lstart < Lstop) && (Rstart < Rstop)){ if (strcmp( words[Rstart]->word, words[Lstart]->word ) < 0) buffer[Bindex++] = words[Rstart++]; else buffer[Bindex++] = words[Lstart++]; } // if (left partition has any remaining elements) while (Lstart < Lstop) buffer[Bindex++] = words[Lstart++]; // We don't actually need this. Think about it. Why not? // // if (right partition has any remaining elements) // while (Rstart < Rstop) // buffer[Bindex++] = words[Rstart++]; // Copy merged data from temporary buffer back into source word list for (int n = 0; n < Bindex; n++) words[start++] = buffer[n]; } // Merge Sort an array of weighted words // words • the array of (weighted_word*)s to sort // start • index of first element to sort // stop • index ONE PAST the last element to sort // buffer • the temporary merge buffer, at least as big as (stop-start+1)/2 // void MergeSortWeightedWords(weighted_word **words, int start, int stop, weighted_word **buffer){ if (start < stop-1){ // -1 because a singleton array is by definition sorted int middle = start + (stop - start) / 2; MergeSortWeightedWords(words, start, middle, buffer); MergeSortWeightedWords(words, middle, stop, buffer); MergeWeightedWords(words, start, middle, stop, buffer); } } // Merge Sort a Dictionary // void MergeSortDict(dict *D){ if (D){ // We only need to allocate a single temporary work buffer, just once, right here. dict * Temp = CreateDict(D->size); if (Temp){ MergeSortWeightedWords(D->wordlist, 0, D->size, Temp->wordlist); } FreeDict(Temp); } } // Main program --------------------------------------------------------------- #include <stdio.h> int main(int argc, char **argv){ // Command-line arguments --> dictionary dict *a_dict = CreateDict(argc-1); for (int n = 1; n < argc; n++) DictAddWord(a_dict, argv[n], 0); // Sort the dictionary MergeSortDict(a_dict); // Print the weighted words for (int n = 0; n < a_dict->size; n++) printf( "%d %s\n", a_dict->wordlist[n]->weight, a_dict->wordlist[n]->word ); // Clean up FreeDict(a_dict); }

int CompareWeightedWords(const weighted_word *a, const weighted_word *b){ int rel = strcmp( a->word, b->word ); if (rel < 0) return -1; if (rel > 0) return 1; return a->weight < b->weight ? -1 : a->weight > b->weight; }