回答編集履歴

- ```C

- #include <stdio.h> // getchar, printf, puts

- #include <stdlib.h> // exit

- #include <string.h> // strchr

-

- void error(const char *s) { printf("Error: %s\n", s); exit(1); }

-

- void error2(int d)

- {

- error(d == '"' ? "string literal not closed" :"character constant not closed");

- }

-

- int parse(int e)

- {

- static char pa[] = "([{", ren[] = ")]}";

- int c;

- char *p;

-

- while ((c = getchar()) != EOF) {

- if (c == '/') {

- if ((c = getchar()) == EOF) return c;

- if (c == '/') // skip "// comment"

- while ((c = getchar()) != EOF && c != '\n') ;

- else if (c == '*') // skip "/* */ comment"

- do {

- while ((c = getchar()) != EOF && c != '*') ;

- error("comment not closed");

- } while (c != '/');

- }

- else if (c == '"' || c == '\'') {

- int d = c, k = 0; // skip string literal or charcter constant

- do {

- if ((c = getchar()) == EOF || c == '\n') error2(d);

- if (c == '\') {

- if ((c = getchar()) == EOF) error2(d);

- if (c == d) c = 0;

- }

- k++;

- } while (c != d);

- if (d == '\'' && (k < 2 || k > 5)) error("bad character constant");

- }

- else if ((p = strchr(pa, c))) { // parse parentheses

- int r = ren[p - pa];

- if (parse(b) != r) error("paren not closed");

- }

- else if (strchr(ren, c)) break;

- }

- return c;

- }

-

- int main(void)

- {

- puts(parse(EOF) == EOF ? "OK" : "unexpected closing paren");

- }

- ```

- バグのご指摘お待ちしています。