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1.6 配列

if (c >= '0' && c <= '9') {

ASCIIコードでは、'0' は 48、'9' は 57、となるので上記のコードは以下と同じ意味となる。

if (c >= 48 && c <= 57) {

c が数字の場合以下のコードの配列の添字は 0 から 9 の範囲の数となる。

ndigit[c-'0'];

演習1-13

#include <stdio.h>

#define IN  1
#define OUT 0
#define MAX_WORD_LENGTH 20

int main(int argc, char *argv[])
{
    int c, i, j, len, state;
    int lword[MAX_WORD_LENGTH];

    state = OUT;
    len = 0;
    for (i = 0; i < MAX_WORD_LENGTH; ++i) {
        lword[i] = 0;
    }

    while ((c = getchar()) != EOF) {
        if (c == ' ' ||
            c == '\n' ||
            c == '\t' ||
            c == ',' ||
            c == '.') {
            if (len > 0) {
                ++lword[len];
            }
            state = OUT;
            len = 0;
        } else if (state == OUT) {
            state = IN;
            ++len;
        } else if (state == IN) {
            ++len;
        }
    }

    printf("length : count\n");

    for (i = 0; i < MAX_WORD_LENGTH; ++i) {
        printf("%6d : ", i+1);
        for (j = 0; j < lword[i+1]; ++j) {
            printf("*");
        }
        printf("\n");
    }

    return 0;
}

実行結果

$ cat bible.txt
Balak puts Balaam to work almost immediately upon arriving. The diviner has Balak build seven altars, on each of which he offers a bull and a ram. The bull and ram are the prime animals to offer because of their value, and the number seven has a long history of being especially propitious. By these offerings, Balaam is trying to ensure his ability to bribe a curse out of God.
$ cat bible.txt | ./ex1-13
length : count
     1 : ****
     2 : ************
     3 : ***************
     4 : *******
     5 : **************
     6 : ********
     7 : *****
     8 : *
     9 : *
    10 : **
    11 : *
    12 : 
    13 : 
    14 : 
    15 : 
    16 : 
    17 : 
    18 : 
    19 : 
    20 : 
$

演習1-14

アルファベット(a-z)のみをカウントし、大文字・小文字の区別はしないようにした。

#include <stdio.h>

#define NALPHABET 24

int main(int argc, char *argv[])
{
    int c, i, j;
    int alphabets[NALPHABET];

    for (i = 0; i < NALPHABET; ++i) {
        alphabets[i] = 0;
    }

    while ((c = getchar()) != EOF) {
        if (c >= 'A' && c <= 'Z') {
            c = c + ('a' - 'A');
            ++alphabets[c - 'a'];
        } else if (c >= 'a' && c <= 'z') {
            ++alphabets[c - 'a'];
        }
    }

    for (i = 0; i < NALPHABET; ++i) {
        printf("%c : ", i+'a');
        for (j = 0; j < alphabets[i]; ++j) {
            printf("*");
        }
        printf("\n");
    }

    return 0;
}

$ cat bible.txt
Balak puts Balaam to work almost immediately upon arriving. The diviner has Balak build seven altars, on each of which he offers a bull and a ram. The bull and ram are the prime animals to offer because of their value, and the number seven has a long history of being especially propitious. By these offerings, Balaam is trying to ensure his ability to bribe a curse out of God.
$ cat bible.txt | ./ex1-14
a : **********************************
b : **************
c : *****
d : *******
e : ********************************
f : **********
g : ******
h : **************
i : ***********************
j : 
k : ***
l : ******************
m : **********
n : ****************
o : *********************
p : ******
q : 
r : ********************
s : *******************
t : *******************
u : ************
v : *****
w : **
x : 
$

プログラミング言語C 第2版 ANSI規格準拠

posted with amazlet at 09.11.27

B.W. カーニハン D.M. リッチー
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