文件上最常见的字母（C编程）

Question

I need to create a function that finds the most common letter in a file using C. Can't figure out my problem, for some reason it always returns [ .

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

char commonestLetter(char* filename);

void main()
{
    char str[101], ch;
    FILE *fout;
    fout = fopen("text.txt", "w");
    if (fout == NULL)
    {
        printf("Can't open file\nIt's probably your fault, worked perfectly on my PC ;)\n");
        fclose(fout);
    }
    printf("Enter string (to be written on file)\n");
    gets(str);
    fputs(str, fout);
    ch = commonestLetter("text.txt");
    printf("The most common letter is %c\n", ch);
    fclose(fout);
}

char commonestLetter(char* filename)
{
    char ch;
    int i, count[26];
    int max = 0, location;
    FILE *f = fopen(filename, "r");
    if (f == NULL)
    {
        printf("file is not open\n");
        return;
    }
    for (i = 0; i < 26; i++)
        count[i] = 0;

    while ((ch = fgetc(f)) != EOF)
    {
        if (isalpha(ch))
            count[toupper(ch) - 'A']++;
    }

    for (i = 0; i < 26; i++)
    {
        if (count[i] >= max)
        {
            max = count[i];
            location = i + 1;
        }
    }
    return location + 'A';
}

Answer 1

Do

location=i;

No need of i+1

As you are doing location+'A';

Suppose the location count[25] has the highest count, so the location becomes 25+1=26 .

Now the return will be 26+65=91 which is of '['

The code of yours is slightly modified but the logic of your is kept

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

char commonestLetter(char* filename);

int main()
{
    char str[101], ch;
    FILE *fout;
    fout = fopen("text.txt", "w");
    if (fout == NULL)
    {
        printf("Can't open file\nIt's probably your fault, worked perfectly on my PC ;)\n");
        return 0;
    }
    printf("Enter string (to be written on file): ");
    fgets(str,sizeof(str),stdin);
    fputs(str, fout);
    fclose(fout);
    ch = commonestLetter("text.txt");
    printf("The most common letter is %c\n", ch);
    return 0;
}

char commonestLetter(char* filename)
{
    char ch;
    int i, count[26];
    int max = 0, location;
    FILE *f = fopen(filename, "r");
    if (f == NULL)
    {
        printf("file is not open\n");
        return;
    }

    memset(&count,0,sizeof(count));
    while ((ch = fgetc(f)) != EOF)
    {
        if (isalpha(ch))
            count[toupper(ch) - 'A']++;
    }

    for (i = 0; i < 26; i++)
    {
        if (count[i] >= max)
        {
            max = count[i];
            location = i;
        }
    }
    fclose(f);
    return location + 'A';
}

Input & Output:

Enter string (to be written on file): Gil this is a testing
The most common letter is I

Answer 2

The problem here is, in your code,

location = i + 1;

location is i+1 at the end, and you're returning location + 'A'; which is (because of your input, probably) (25+1) + 'A' , ie, 26 + 'A' which is [ .