これは単純な関数 (文字列内の一意の文字数をカウントする) のはずですが、奇妙な問題が発生しています。私のコードの使用では、ASCII 文字の az と AZ のみが想定されていることに注意してください。
int unique_chars(char* my_str) {
//printf("starting unique_chars\n");
char seen_buffer[52]; // max 52 letters a-z & A-Z
int seen_count = 1; // not ever expecting my_str to be NULL
int i, j;
char next;
//printf("first char is %c\n", my_str[0]);
seen_buffer[0] = my_str[0]; // first char must be unique
for (i=1; i<strlen(my_str); i++) { // walk along the rest of my_str
next = my_str[i];
if (next >= 97) {
next = next - 32; // the next char will always be capital, for convenience
}
for (j=0; j<seen_count; j++) { // compare next to all the unique chars seen before
//printf("current char is %c, checking against %c\n", next, seen_buffer[j]);
if ((next==seen_buffer[j]) || (next+32==seen_buffer[j])) {
//printf("breaking\n");
break; // jump to the next char in my_str if we find a match
}
if (j==seen_count-1) { // at this point, we're sure that next hasn't been seen yet
//printf("new unique char is %c\n", next);
seen_count++;
seen_buffer[seen_count] = next;
//printf("new char val is %c, should be %c\n", seen_buffer[seen_count], next);
break;
}
}
}
return seen_count;
}
int main(int argc, char* argv[]){
char* to_encode = argv[1];
printf("unique chars: %d\n", unique_chars(to_encode));
}
特定の文字列で呼び出すと、間違った結果が得られます。たとえば、次を試してください。
./a.out gghhiijj
これにより、(printfのコメントが解除された状態で)次の結果が得られます。
starting unique_chars
first char is g
current char is G, checking against g
breaking
current char is H, checking against g
new unique char is H
new char val is H, should be H
current char is H, checking against g
current char is H, checking against
new unique char is H
new char val is H, should be H
current char is I, checking against g
current char is I, checking against
current char is I, checking against H
new unique char is I
new char val is I, should be I
current char is I, checking against g
current char is I, checking against
current char is I, checking against H
current char is I, checking against H
new unique char is I
new char val is I, should be I
current char is J, checking against g
current char is J, checking against
current char is J, checking against H
current char is J, checking against H
current char is J, checking against I
new unique char is J
new char val is J, should be J
current char is J, checking against g
current char is J, checking against
current char is J, checking against H
current char is J, checking against H
current char is J, checking against I
current char is J, checking against I
new unique char is J
new char val is J, should be J
そのため、seen_buffer に重複が発生し続けます。そこにあるはずのアルファベット文字ではなく、空白文字がそこに格納されているからです。しかし、seen_buffer に書き込んだ直後に比較を行うと (つまり、新しい char val は %c で、%c\n である必要があります)、正しい char が表示されます!
どんな助けでも大歓迎です!