read txt, count each alphabet using linked list - c

Question

#pragma warning (disable:4996)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <ctype.h>
#define NUM_OF_ALPHABET 26
#define MAX_HEAP_SIZE 100
typedef struct _CharFrequency
{
char character;
int frequency;
struct _CharFrequency * next;
}CharFrequency;
typedef CharFrequency* pCharFrequency;
pCharFrequency pHead = NULL;
void initList();
void addNode(char ch);
void printAllNode(pCharFrequency pHead);
int main()
{
int i = 0, cnt = 0;
FILE *pFile;
char readLine[1024], *ptr;
char *token = " \t\n.";
pFile = fopen("C:\\Users\\Home\\Desktop\\dataset.txt", "r");
if (pFile == NULL)
{
printf("File open failed.\n");
return 0;
}
while (fgets(readLine, 1024, pFile) != NULL)
{
ptr = strtok(readLine, token);
while (ptr != NULL)
{
for (i = 0; i < strlen(ptr); i++)
{
addNode(ptr[i]);
}
ptr = strtok(NULL, token);
}
}
printAllNode(pHead);
return 0;
}
void initList()
{
pHead = (CharFrequency*)malloc(sizeof(CharFrequency));
if (!pHead)
{
printf("Fault\n");
return;
}
pHead->character = '\0';
pHead->frequency = 0;
pHead->next = NULL;
}
void addNode(char ch)
{
int i = 0;
pCharFrequency pNode = NULL;
pCharFrequency pCurrent= NULL;
if (isalpha(ch) == 0)
return;
if (ch >= 'A' && ch <= 'Z')
ch = ch + 32;
printf("%c ", ch);
for (pCurrent = pHead; pCurrent != NULL ; pCurrent = pCurrent->next)
{
if (pCurrent->character == ch)
{
pCurrent->frequency++;
}
else
{
pNode = (CharFrequency*)malloc(sizeof(CharFrequency));
pNode->frequency = 0;
pNode->next = NULL;
pNode->character = ch;
pNode->frequency++;
pCurrent->next = pNode;
}
}
pNode = (CharFrequency*)malloc(sizeof(CharFrequency));
pNode->frequency = 0;
pNode->next = NULL;
pNode->character = ch;
pNode->frequency++;
pCurrent->next = pNode;
}
void printAllNode(pCharFrequency pHead)
{
pCharFrequency pCurrent;
pCurrent = pHead;
pCurrent = pHead;
while (pCurrent->next != NULL) {
printf("%c %d", pCurrent->character, pCurrent->frequency);
pCurrent = pCurrent->next;
}
}
I want to build a program that reads txt file, count only alphabet, and count them using linked list. I make struct called CharFrequency to count alphabet.
addNode function gets the character, checks if it's in the list or not, and count them.
It makes error when doing for() in the addNode function.

Answer 1

You need to rethink about the logic inside your addNode method. It is adding a new node every time a character is not found in the list, and even if a match is found,the loop will continue until the last node adding a new node every time.
You could do something like this to get you started and experiment on it to make it more efficient.
pCharFrequency pNode = NULL;
pCharFrequency pCurrent= NULL;
pCharFrequency pTail= NULL;//this will keep track of the last node in the list
//so that we use it to insert a new node
....//your other code
pCurrent = pHead;//start from the head
while (pCurrent!=NULL)
{
if (pCurrent->character == ch)
{
pCurrent->frequency++;
return;//if a match was found, count and return
}
if(pCurrent->next == NULL)
pTail=pCurrent;//save the pointer to the last node in the list if we reach to it
pCurrent=pCurrent->next;//get the next node
}
//if we reach here, then we need to create a new node
pNode = (CharFrequency*)malloc(sizeof(CharFrequency));
if(pNode==NULL)
{
//show error message
return;
}
pNode->frequency = 1;
pNode->next = NULL;
pNode->character = ch;
if(pHead==NULL)
pHead=pNode;//for the very first node,we just assign to head
else
pTail->next = pNode;//otherwise set the last node's next to the node we just created