Data commit

Task/24-game/C/24-game.c

@@ -0,0 +1,281 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <stdlib.h>
+#include <setjmp.h>
+#include <time.h>
+
+jmp_buf ctx;
+const char *msg;
+
+enum { OP_NONE = 0, OP_NUM, OP_ADD, OP_SUB, OP_MUL, OP_DIV };
+
+typedef struct expr_t *expr, expr_t;
+struct expr_t {
+	int op, val, used;
+	expr left, right;
+};
+
+#define N_DIGITS 4
+expr_t digits[N_DIGITS];
+
+void gen_digits()
+{
+	int i;
+	for (i = 0; i < N_DIGITS; i++)
+		digits[i].val = 1 + rand() % 9;
+}
+
+#define MAX_INPUT 64
+char str[MAX_INPUT];
+int pos;
+
+#define POOL_SIZE 8
+expr_t pool[POOL_SIZE];
+int pool_ptr;
+
+void reset()
+{
+	int i;
+	msg = 0;
+	pool_ptr = pos = 0;
+	for (i = 0; i < POOL_SIZE; i++) {
+		pool[i].op = OP_NONE;
+		pool[i].left = pool[i].right = 0;
+	}
+	for (i = 0; i < N_DIGITS; i++)
+		digits[i].used = 0;
+}
+
+/* longish jumpish back to input cycle */
+void bail(const char *s)
+{
+	msg = s;
+	longjmp(ctx, 1);
+}
+
+expr new_expr()
+{
+	if (pool_ptr < POOL_SIZE)
+		return pool + pool_ptr++;
+	return 0;
+}
+
+/* check next input char */
+int next_tok()
+{
+	while (isspace(str[pos])) pos++;
+	return str[pos];
+}
+
+/* move input pointer forward */
+int take()
+{
+	if (str[pos] != '\0') return ++pos;
+	return 0;
+}
+
+/* BNF(ish)
+expr = term { ("+")|("-") term }
+term = fact { ("*")|("/") expr }
+fact =	number
+	| '(' expr ')'
+*/
+
+expr get_fact();
+expr get_term();
+expr get_expr();
+
+expr get_expr()
+{
+	int c;
+	expr l, r, ret;
+	if (!(ret = get_term())) bail("Expected term");
+	while ((c = next_tok()) == '+' || c == '-') {
+		if (!take()) bail("Unexpected end of input");
+		if (!(r = get_term())) bail("Expected term");
+
+		l = ret;
+		ret = new_expr();
+		ret->op = (c == '+') ? OP_ADD : OP_SUB;
+		ret->left = l;
+		ret->right = r;
+	}
+	return ret;
+}
+
+expr get_term()
+{
+	int c;
+	expr l, r, ret;
+	ret = get_fact();
+	while((c = next_tok()) == '*' || c == '/') {
+		if (!take()) bail("Unexpected end of input");
+
+		r = get_fact();
+		l = ret;
+		ret = new_expr();
+		ret->op = (c == '*') ? OP_MUL : OP_DIV;
+		ret->left = l;
+		ret->right = r;
+	}
+	return ret;
+}
+
+expr get_digit()
+{
+	int i, c = next_tok();
+	expr ret;
+	if (c >= '0' && c <= '9') {
+		take();
+		ret = new_expr();
+		ret->op = OP_NUM;
+		ret->val = c - '0';
+		for (i = 0; i < N_DIGITS; i++)
+			if (digits[i].val == ret->val && !digits[i].used) {
+				digits[i].used = 1;
+				return ret;
+			}
+		bail("Invalid digit");
+	}
+	return 0;
+}
+
+expr get_fact()
+{
+	int c;
+	expr l = get_digit();
+	if (l) return l;
+	if ((c = next_tok()) == '(') {
+		take();
+		l = get_expr();
+		if (next_tok() != ')') bail("Unbalanced parens");
+		take();
+		return l;
+	}
+	return 0;
+}
+
+expr parse()
+{
+	int i;
+	expr ret = get_expr();
+	if (next_tok() != '\0')
+		bail("Trailing garbage");
+	for (i = 0; i < N_DIGITS; i++)
+		if (!digits[i].used)
+			bail("Not all digits are used");
+	return ret;
+}
+
+typedef struct frac_t frac_t, *frac;
+struct frac_t { int denom, num; };
+
+int gcd(int m, int n)
+{
+	int t;
+	while (m) {
+		t = m; m = n % m; n = t;
+	}
+	return n;
+}
+
+/* evaluate expression tree.  result in fraction form */
+void eval_tree(expr e, frac res)
+{
+	frac_t l, r;
+	int t;
+	if (e->op == OP_NUM) {
+		res->num = e->val;
+		res->denom = 1;
+		return;
+	}
+
+	eval_tree(e->left, &l);
+	eval_tree(e->right, &r);
+
+	switch(e->op) {
+	case OP_ADD:
+		res->num = l.num * r.denom + l.denom * r.num;
+		res->denom = l.denom * r.denom;
+		break;
+	case OP_SUB:
+		res->num = l.num * r.denom - l.denom * r.num;
+		res->denom = l.denom * r.denom;
+		break;
+	case OP_MUL:
+		res->num = l.num * r.num;
+		res->denom = l.denom * r.denom;
+		break;
+	case OP_DIV:
+		res->num = l.num * r.denom;
+		res->denom = l.denom * r.num;
+		break;
+	}
+	if ((t = gcd(res->denom, res->num))) {
+		res->denom /= t;
+		res->num /= t;
+	}
+}
+
+void get_input()
+{
+	int i;
+reinput:
+	reset();
+	printf("\nAvailable digits are:");
+	for (i = 0; i < N_DIGITS; i++)
+		printf(" %d", digits[i].val);
+	printf(". Type an expression and I'll check it for you, or make new numbers.\n"
+		"Your choice? [Expr/n/q] ");
+
+	while (1) {
+		for (i = 0; i < MAX_INPUT; i++) str[i] = '\n';
+		fgets(str, MAX_INPUT, stdin);
+		if (*str == '\0') goto reinput;
+		if (str[MAX_INPUT - 1] != '\n')
+			bail("string too long");
+
+		for (i = 0; i < MAX_INPUT; i++)
+			if (str[i] == '\n') str[i] = '\0';
+		if (str[0] == 'q') {
+			printf("Bye\n");
+			exit(0);
+		}
+		if (str[0] == 'n') {
+			gen_digits();
+			goto reinput;
+		}
+		return;
+	}
+}
+
+int main()
+{
+	frac_t f;
+	srand(time(0));
+
+	gen_digits();
+	while(1) {
+		get_input();
+		setjmp(ctx); /* if parse error, jump back here with err msg set */
+		if (msg) {
+			/* after error jump; announce, reset, redo */
+			printf("%s at '%.*s'\n", msg, pos, str);
+			continue;
+		}
+
+		eval_tree(parse(), &f);
+
+		if (f.denom == 0) bail("Divide by zero");
+		if (f.denom == 1 && f.num == 24)
+			printf("You got 24.  Very good.\n");
+		else {
+			if (f.denom == 1)
+				printf("Eval to: %d, ", f.num);
+			else
+				printf("Eval to: %d/%d, ", f.num, f.denom);
+			printf("no good.  Try again.\n");
+		}
+	}
+	return 0;
+}