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//#define _GNU_SOURCE
#include <regex.h>
#include <search.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define arrlen(x) (sizeof(x)/sizeof((x)[0]))
enum operation {
OP_VAL,
OP_ADD,
OP_SUB,
OP_MUL,
OP_DIV,
};
enum operation
operation_get(char op)
{
switch (op) {
case '+': return OP_ADD;
case '-': return OP_SUB;
case '*': return OP_MUL;
case '/': return OP_DIV;
}
return OP_VAL;
}
struct monkey {
char name[5];
enum operation op;
long value;
char left[5];
char right[5];
};
struct monkey *
monkey_create_val(char const * name, long value)
{
struct monkey * m;
if (!name || strlen(name) != 4)
return NULL;
if ((m = malloc(sizeof(struct monkey))) == NULL)
return NULL;
snprintf(m->name, sizeof(m->name), "%s", name);
m->op = OP_VAL;
m->value = value;
m->left[0] = '\0';
m->right[0] = '\0';
return m;
}
struct monkey *
monkey_create_op(char const * name, enum operation op, char const * left, char const * right)
{
struct monkey * m;
if (!name || strlen(name) != 4
|| op == OP_VAL
|| !left || strlen(left) != 4
|| !right || strlen(right) != 4)
return NULL;
if ((m = malloc(sizeof(struct monkey))) == NULL)
return NULL;
snprintf(m->name, sizeof(m->name), "%s", name);
m->op = op;
m->value = 0;
snprintf(m->left, sizeof(m->left), "%s", left);
snprintf(m->right, sizeof(m->right), "%s", right);
return m;
}
int
monkey_cmp(struct monkey const * a, struct monkey const * b)
{
return strcmp(a->name, b->name);
}
int
monkey_cmp_t(void const * a, void const * b)
{
return monkey_cmp(a, b);
}
struct monkey *
monkey_find(void * monkey_tree, char const * name)
{
struct monkey tmp, ** result;
if (!name || strlen(name) != 4) {
fprintf(stderr, "Invalid monkey name %s\n", name ? name : "(null)");
return NULL;
}
snprintf(tmp.name, sizeof(tmp.name), "%s", name);
result = tfind(&tmp, &monkey_tree, monkey_cmp_t);
return result ? *result : NULL;
}
long
monkey_value(void * monkey_tree, struct monkey * m)
{
long v;
if (!m) {
fprintf(stderr, "%s: Bad monkey\n", __FUNCTION__);
return 0;
}
switch (m->op) {
case OP_VAL:
v = m->value;
break;
case OP_ADD:
v = monkey_value(monkey_tree, monkey_find(monkey_tree, m->left))
+ monkey_value(monkey_tree, monkey_find(monkey_tree, m->right));
break;
case OP_SUB:
v = monkey_value(monkey_tree, monkey_find(monkey_tree, m->left))
- monkey_value(monkey_tree, monkey_find(monkey_tree, m->right));
break;
case OP_MUL:
v = monkey_value(monkey_tree, monkey_find(monkey_tree, m->left))
* monkey_value(monkey_tree, monkey_find(monkey_tree, m->right));
break;
case OP_DIV:
v = monkey_value(monkey_tree, monkey_find(monkey_tree, m->left))
/ monkey_value(monkey_tree, monkey_find(monkey_tree, m->right));
break;
default:
fprintf(stderr, "Unexpected operation for %s: %d\n", m->name, m->op);
return 0;
}
return v;
}
int
main()
{
regex_t reval, reop;
char buf[BUFSIZ];
void * monkey_tree = NULL;
if (regcomp(&reval, "([[:alpha:]]{4}): (-?[[:digit:]]+)", REG_EXTENDED) != 0
|| regcomp(&reop, "([[:alpha:]]{4}): ([[:alpha:]]{4}) ([-+*/]) ([[:alpha:]]{4})", REG_EXTENDED) != 0)
{
fprintf(stderr, "Bad regex\n");
return -1;
}
while (fgets(buf, sizeof(buf), stdin)) {
regmatch_t matches[5];
struct monkey * m;
if (regexec(&reval, buf, arrlen(matches), matches, 0) == 0) {
buf[matches[1].rm_eo] = '\0';
m = monkey_create_val(buf + matches[1].rm_so, atoi(buf + matches[2].rm_so));
}
else if (regexec(&reop, buf, arrlen(matches), matches, 0) == 0) {
buf[matches[1].rm_eo] = '\0';
buf[matches[2].rm_eo] = '\0';
buf[matches[4].rm_eo] = '\0';
m = monkey_create_op(buf + matches[1].rm_so,
operation_get(buf[matches[3].rm_so]),
buf + matches[2].rm_so,
buf + matches[4].rm_so);
}
else {
fprintf(stderr, "Bad monkey: %s\n", buf);
regfree(&reop);
regfree(&reval);
return -1;
}
tsearch(m, &monkey_tree, monkey_cmp_t);
}
printf("root value: %ld\n", monkey_value(monkey_tree, monkey_find(monkey_tree, "root")));
#ifdef _GNU_SOURCE
tdestroy(monkey_tree, free);
#endif
regfree(&reop);
regfree(&reval);
return 0;
}
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