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I need help counting the number of times a letter appears in a string, for a-z

This is a discussion on I need help counting the number of times a letter appears in a string, for a-z within the C Programming forums, part of the General Programming Boards category; I recently got an assignment to input a string and count how many times each letter appears in the alphabet. ...

  1. #1
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    Lightbulb I need help counting the number of times a letter appears in a string, for a-z

    I recently got an assignment to input a string and count how many times each letter appears in the alphabet. First I have to set all letters to Caps, then convert all ASCII numbers to 0 through 25 (A = 0 instead of 65). Finally, I have to count how many times each letter appears. I need help on this last part because the first two are easy. I found this code pasted 9 years ago:

    Code:
    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
    #define MAX_LENGTH 256 #include <stdio.h> int main() { char sentance[MAX_LENGTH]; // Holds the sentance int x = 0; // Holds the current posistion for the search int y = 0; // Holds total number of a's found printf("Enter a sentance\n"); // Gets input fgets(sentance, MAX_LENGTH, stdin); while(sentance[x] != '\0') { // Loop threw sentance if(sentance[x] == 'a') // Chech to see if the current character is a a ++y; // It is, add one to y ++x; // Update posistion } printf("\nThere are %i letter a's in your sentance\n", y); // Print answer return 0; } // Wonder why I did c++ comments in c code when I dont do c++
    Now this would work except I'm not allowed to use 26 If statements. Anyone have any ideas?

    P.S. - One idea I have is making another array so I don't have 26 variables for each letter of the alphabet, so exampleArray[26] = 0;
    But, I don't know how you would assign, say, the letter A to 1 and then If exampleArray[1] = A then (Acount++). But, this would just lead to another 26 If statements. Any help would be appreciated. Thanks.

    [NOTE: This is pseudocode and I'm just giving an idea of what it would do.]
    Last edited by cleo641; 11-01-2012 at 05:55 PM. Reason: Forgot to add something

  2. #2
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    Here's a valuable trick for your programmer toolkit: many times the key to working through a problem can be solved using some relationship between the index of the array being used, and something about the data.

    You've got that already, built into the assignment - 26 letters (you posted "numbers" by the way), and 26 indices, 0-25. 26 in all.



    You'll need one for or while loop. Not much else.

    Code:
    for(each letter in the string array str[]) {
       //change the letter to uppercase
       arrayNumber[str[i]-'A']++;     //there's the trick
    }
    You won't probably visualize that kind of logic just yet, but study it, and verify that it works - and remember it.
    laserlight and stahta01 like this.

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    Is there any way to message you my actual code? I'd like to private message it to you.

  4. #4
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    I'd rather you posted it, since this is a public forum. Better, surely.

    But you can post up only the part of the code that is giving you trouble - or you have a question about - but please describe any problem. "Doesn't work" is far too brief, for example.

    I'd suggest responding faster than 2 days, because threads here, have a relatively short attention span, and quickly get pushed down and onto page two. Page two and beyond is a bit of a graveyard for threads.

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    Sorry to announce this to you, but I figured it out (with help from Teacher). Thanks for your help. I really appreciate it. It makes a lot more sense now that I have it. It seems so obvious but I usually think outside the box and often speculate on multiple answers, especially more complex ones. Anyway, take care.

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