P113WordFrequency.c

// Program P11.3

#include <stdio.h>
#include <ctype.h>
#include <string.h>
#define MaxWordSize 20
#define MaxWords 10
#define N 13
#define Empty ""
typedef struct {
	char word[MaxWordSize + 1];
	int freq, next;
} WordInfo;

int main() {
	int getWord(FILE *, char[]);
	void printResults(FILE *, WordInfo [], int);
	int search(WordInfo [], char []);
	int addToTable(WordInfo [], char [], int, int);
	char word[MaxWordSize+1];
	WordInfo wordTable[N+1]; //N - table size

	for (int h = 1; h <= N; h++) strcpy(wordTable[h].word, Empty);

	FILE * in = fopen("wordFreq.in", "r");
	FILE * out = fopen("wordFreq.out", "w");

	int first = -1; //points to first word in alphabetical order
	int numWords = 0;

	while (getWord(in, word) != 0) {
		int loc = search(wordTable, word);
		if (loc > 0) wordTable[loc].freq++;
		else //this is a new word
			if (numWords < MaxWords) { //if table is not full
				first = addToTable(wordTable, word, -loc, first);
				++numWords;
			}
			else fprintf(out, "'%s' not added to table\n", word);
	}
	printResults(out, wordTable, first);
	fclose(in);
	fclose(out);
} // end main

int getWord(FILE * in, char str[]) {
// stores the next word, if any, in str; word is converted to lowercase
// returns 1 if a word is found; 0, otherwise
	char ch;
	int n = 0;
	// read over non-letters
	while (!isalpha(ch = getc(in)) && ch != EOF) ; //empty while body
	if (ch == EOF) return 0;
	str[n++] = tolower(ch);
	while (isalpha(ch = getc(in)) && ch != EOF)
		if (n < MaxWordSize) str[n++] = tolower(ch);
	str[n] = '\0';
	return 1;
} // end getWord

int search(WordInfo table[], char key[]) {
//search for key in table; if found, return its location; if not,
//return -loc if it must be inserted in location loc
	int convertToNumber(char []);
	int keyNum = convertToNumber(key);
	int loc = keyNum % N + 1;
	int k = keyNum % (N - 2) + 1;

	while ((strcmp(table[loc].word, Empty) != 0) &&
					(strcmp(table[loc].word, key) != 0)) {
		loc = loc + k;
		if (loc > N) loc = loc - N;
	}
	if (strcmp(table[loc].word, Empty) == 0) return -loc;
	return loc;
} // end search

int convertToNumber(char key[]) {
	int h = 0, keyNum = 0, w = 3;
	while (key[h] != '\0') {
		keyNum += w * key[h++];
		w = w + 2;
	}
	return keyNum;
} //end convertToNumber

int addToTable(WordInfo table[], char key[], int loc, int head) {
//stores key in table[loc] and links it in alphabetical order
	strcpy(table[loc].word, key);
	table[loc].freq = 1;
	int curr = head;
	int prev = -1;
	while (curr != -1 && (strcmp(key, table[curr].word) > 0)) {
		prev = curr;
		curr = table[curr].next;
	}
	table[loc].next = curr;
	if (prev == -1) return loc; //new first item
	table[prev].next = loc;
	return head; //first item did not change
} //end addToTable

void printResults(FILE *out, WordInfo table[], int head) {
	fprintf(out, "\nWords        Frequency\n\n");
	while (head != -1) {
		fprintf(out, "%-15s %2d\n", table[head].word, table[head].freq);
		head = table[head].next;
	}
} //end printResults