Segmentation Fault (Core Dumped)

Hi guys,

I am writing a program that needs to do a few things with an input string:
-Replace all lower case vowels (a, e, i, o, u) with the letter ‘a’.
-Add to each word that starts with a consonant the letters “ay” at the front of this word.
-Place the first two words at the end of the sentence.

I have written the next code, but I keep getting a segmentation fault. I have tried to execute the functions one by one, but I haven't come very far with that. Could someone please help me?

Code:

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#include <stdio.h>
#include <string.h>
#define lengthstr 32


void replaceVowels(char str[]);
void replaceChars(char str[], char sChar, char rChar);
void expandString(char str[], char aChar[], int index);
void addAY(char str[]);
int findFO(char str[], char aChar);
void reorderString(char str[], char index0, char index1);






void main(void)
{
   
 char myString[lengthstr]; 


 printf("** Welcome to the Double Dutch game\n");
 printf("Please enter a string: ");
 scanf("%[^\n]s", myString);
 printf("%s\n", myString);
 replaceVowels(myString);
 addAY(myString);
 expandString(myString, " ", strlen(myString));
 
 int index0 = findFO(myString, ' ');
 myString[index0] = '+';
 
 int index1 = findFO(myString, ' ');
 myString[index1] = '+';
 
 reorderString(myString, index0, index1);
 
 replaceChars(myString, '+', ' ');
 
 printf("Double Dutch translation: %s\n", myString);
}




void replaceVowels(char str[])
{
    int i;
   
    for(i = 0; str[i] != '\0'; i++)
    {
        if(str[i] == 'e'||str[i] == 'i'||str[i] == 'o'||str[i] == 'u')
        {
            str[i] = 'a';
        }
       
    }
   
}


void replaceChars(char str[], char sChar, char rChar)
{
    int i = findFO(str, sChar);
   
    while(i >= 0)
    {
    str[i] = rChar;
    i = findFO(str, sChar);
    }
}




void expandString(char str[], char aChar[], int index)
{


 char str2[30];
 
 strncpy(str2, str, index);
 
 int length = strlen(str2);
 
 length = length + strlen(aChar);
 strcpy(str2+length, str+index);
 
 strcpy(str, str2);
   
 }
 
 void addAY(char str[])
 {
    int i;
   
    if(str[0] != 'a'&&str[0] != 'e'&&str[0] != 'o'&str[0] != 'u'&&str[0] != 'I')
    {
        expandString(str, "ay", 0);
    }
   
    i = findFO(str, ' ');
   
    while(i >= 0)
    {
        str[i] = '+';
       
        if(str[i+1] != 'a'&&str[i+1] != 'e'&&str[i+1] != 'o'&str[i+1] != 'u'&&str[i+1] != 'I')
        {
          expandString(str, "ay", i+1); 
        }
       
        i = findFO(str, ' ');
    }
   
    replaceChars(str, '+', ' ');
 }
   


int findFO(char str[], char aChar)
{
    int p = 0;
    int i = 0;
   
    while(i < strlen(str))
    {
    if(str[i] == aChar)
    {
      p = 1;
      break;
    }
    i++;
    }
   
    if(p == 1)
    {
        return i;
    }
   
    else
    {
        return -1;
    }
   
}


void reorderString(char str[], char index0, char index1)
{
    char string0[strlen(str)];
    char string1[strlen(str)];
    char string2[strlen(str)];
   
    strncpy(string0, str, index0);
    strncpy(string1, str+index0, index1-index0);
    strncpy(string2, str+index1, strlen(str)-index1);
   
    strcpy(str, string2);
    strcat(str, string0);
    strcat(str, string1);
   
}

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A couple of things to look out for.
1. char string1[strlen(str)];
This doesn't allocate enough space to copy str. You need to add 1 for the \0 as well.
2. Strncpy doesn't automatically append a \0, so these strings might be longer than you think.

Read: FAQ > main() / void main() / int main() / int main(void) / int main(int argc, char *argv[]) - Cprogramming.com

Something is wrong here:

Code:

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if(str[0] != 'a'&&str[0] != 'e'&&str[0] != 'o'&str[0] != 'u'&&str[0] != 'I')

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