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Isogram

Intro

An isogram (also known as a "nonpattern word") is a word or phrase without a repeating letter, however spaces and hyphens are allowed to appear multiple times.

Examples of isograms:

  • lumberjacks
  • background
  • downstream
  • six-year-old

The word isograms, however, is not an isogram, because the s repeats.

Task

Determine if a word or phrase is an isogram.

The Code

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#include "isogram.h"
#include "string.h"
#include "ctype.h"


bool is_isogram(const char phrase[])
{
    int length;
    if(phrase==NULL)return false;

    for(length=0;phrase[length]!='\0';length++);
    if (length==0)return true;

    int i;
    for(i=0;i<length;i++){
        int ii;
        if( isalpha(phrase[i])==false)continue;
        for(ii=i+1;ii<length;ii++)
        {
            if(tolower(phrase[i])==tolower(phrase[ii])) return false;
        }
    }

    return true;
}

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#ifndef ISOGRAM_H
#define ISOGRAM_H

#include <stdbool.h>

bool is_isogram(const char phrase[]);

#endif
Last update: February 8, 2021

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