/*
  Name:    ex8-16.c
  Purpose: anagram tester
  Author:  Bill Slough
*/

#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>

#define N 15          /* maximum length of each input word */
#define ALPHSIZE 26   /* number of letters in the alphabet */

int getline(char a[ ], int size, bool *overflow);
void changeCase(char a[ ], int n);
bool allZeros(int x[ ], int n);

int main() {
    char firstWord[N];         /* arrays for each of the words */
    char secondWord[N];
    int firstLength;           /* length of each word */
    int secondLength;
    bool overflow;             /* buffer over-run? */
    int freq[ALPHSIZE] = {0};  /* all 0's initially */
    int i;
    char ch;

    /* Get the first word */
    printf("Enter first word: ");
    firstLength = getline(firstWord, N, &overflow);

    /* Terminate execution if there were too many input characters */
    if (overflow) {
        printf("Error in input: buffer overflow.\n");
        return 1;
    }

    /* Get the second word */
    printf("Enter second word: ");
    secondLength = getline(secondWord, N, &overflow);

     /* Terminate execution if there were too many input characters */
    if (overflow) {
        printf("Error in input: buffer overflow.\n");
        return 1;
    }

    if (firstLength != secondLength)
        printf("The words are not anagrams -- mismatched lengths.\n");

    /* ensure both words are of the same case */
    changeCase(firstWord, firstLength);
    changeCase(secondWord, secondLength);

    /* determine letter frequency in the first word */
    for (i = 0; i < firstLength; i++) {
        ch = firstWord[i];
        if (isalpha(ch))
            freq[ch - 'a']++;     /* boost count for this letter */
    }

    /* do the same for the second word, this time decreasing counts */
    for (i = 0; i < secondLength; i++) {
        ch = secondWord[i];
        if (isalpha(ch))
            freq[ch - 'a']--;
    }

    if (allZeros(freq, ALPHSIZE))
        printf("The words are anagrams.\n");
    else
        printf("The words are not anagrams.\n");
    
    return 0;
}


/* Read a line of characters into the array a, which has capacity = size  */
int getline(char a[ ], int size, bool *overflow) {
    int i;
    char ch;
    i = 0;
    while (i < size && (ch = getchar()) != '\n') {
        a[i++] = ch;
    }
    *overflow =  (i == size) && (getchar() != '\n');
    return i;
}

/* Replace the letters in a word with its lower-case counterparts */
void changeCase(char a[ ], int n) {
    int i;
    for (i = 0; i < n; i++) {
        a[i] = tolower(a[i]);
    }
}

/* is every element of a given array zero? */
bool allZeros(int x[ ], int n) {
    int i;
    for (i = 0; i < n; i++)
        if (x[i] != 0)
            return false;
    return true;
}