2020 day 19 part 1 (C) - won't work for part 2 !!
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224
2020/day19/aoc-c.c
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224
2020/day19/aoc-c.c
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/* aoc-c.c: Advent2020, day 23, part 1
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <ctype.h>
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#include "list.h"
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#include "debug.h"
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#define MAX_RULES 256
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#define MAX_MSG 512
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/* to simplify code, we consider here that :
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* - a rule has no more than 3 sub-rules
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* - there are at most 2 possible sub-rules per rule
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*/
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struct subrule {
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int rule[2][3];
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};
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static struct rule {
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enum type {
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SUB,
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CHR
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} type;
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struct subrule sub;
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int str;
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} rules[MAX_RULES] = {
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[0 ... (MAX_RULES-1)] = {
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.sub.rule = {{-1, -1, -1}, {-1, -1, -1}}
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}
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};
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static char *mesg[MAX_MSG];
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static int nrules, nmesg;
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static void printall()
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{
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for (int i = 0; i < nrules; ++i) {
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printf("rule %3d : ", i);
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if (rules[i].type == CHR) {
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printf("[%c]\n", rules[i].str);
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continue;
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}
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for (int j = 0; j < 3 && rules[i].sub.rule[0][j] != -1; ++j)
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printf("%d ", rules[i].sub.rule[0][j]);
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for (int j = 0; j < 3 && rules[i].sub.rule[1][j] != -1; ++j)
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printf("%s%d ", j? "": "| ", rules[i].sub.rule[1][j]);
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printf("\n");
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}
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for (int i = 0; i < nmesg; ++i) {
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printf("%3d: %s\n", i, mesg[i]);
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}
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}
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/**
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* parse - parse input.
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*/
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static void parse()
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{
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size_t alloc;
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ssize_t len;
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char *buf = NULL, *tok;
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int rule;
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while ((len = getline(&buf, &alloc, stdin)) > 0) {
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int or = 0, sub = 0;
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buf[--len] = 0;
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if (len == 0)
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continue;
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if (isalpha(*buf)) { /* message */
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mesg[nmesg++] = strdup(buf);
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} else { /* rule */
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if (!(tok = strtok(buf, ": "))) /* rule number */
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continue;
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nrules++;
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rule = atoi(tok);
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while ((tok = strtok(NULL, ":\" "))) {
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switch (*tok) {
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case 'a': /* final rule */
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case 'b':
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rules[rule].type = CHR;
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rules[rule].str = *tok;
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goto nextline;
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case '|': /* second ruleset */
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or++;
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sub = 0;
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break;
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default:
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rules[rule].type = SUB;
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rules[rule].sub.rule[or][sub] = atoi(tok);
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sub++;
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break;
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}
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}
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}
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nextline: ;
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}
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free(buf);
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}
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static int match(char *str, int *pos, int rule, int depth)
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{
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struct rule *r = rules+rule;
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int found = 0, postmp = *pos;
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char *space = " ";
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log_f(3, "%.*sstr=%s pos=%d rule=%d\n", depth * 2, space, str, *pos, rule);
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/* check for no char left ? */
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//if (!str[*pos]) {
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// printf("No char left !\n");
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// found = 0;
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// goto end;
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//}
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switch (r->type) {
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case SUB:
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found = 1;
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log_f(3, "%.*sLEFT\n", depth * 2, space);
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for (int sub = 0; sub < 3 && r->sub.rule[0][sub] >= 0; ++sub) {
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if (!match(str, pos, r->sub.rule[0][sub], depth + 1)) {
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*pos = postmp;
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found = 0;
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break;
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}
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}
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if (found || r->sub.rule[1][0] == -1)
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goto end;
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log_f(3, "%.*sRIGHT\n", depth * 2, space);
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found = 1;
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for (int sub = 0; sub < 3 && r->sub.rule[1][sub] >= 0; ++sub) {
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if (!match(str, pos, r->sub.rule[1][sub], depth + 1)) {
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*pos = postmp;
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found = 0;
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goto end;
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}
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}
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goto end;
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case CHR:
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if (rules[rule].str == str[*pos]) {
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(*pos)++;
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found = 1;
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goto end;
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}
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found = 0;
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goto end;
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}
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end:
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/* check for exact length */
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if (depth == 0 && str[*pos]) {
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log_f(3, "chars remaining !\n");
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found = 0;
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}
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log_f(3, "%.*sstr=%s pos=%d rule=%d ret=%s\n", depth * 2, space, str+*pos, *pos, rule, found? "ok":
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"NOK");
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return found; /* not reached */
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}
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static long part1()
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{
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int ok = 0, pos;
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for (int msg = 0; msg < nmesg; ++msg) {
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pos = 0;
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if (match(mesg[msg], &pos, 0, 0)) {
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printf("%s: ok\n", mesg[msg]);
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ok++;
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} else {
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printf("%s: NOK\n", mesg[msg]);
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}
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}
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return ok;
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}
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static long part2()
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{
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static const struct subrule new[2] = {
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{{{42, -1, -1}, {42, 8, -1}}},
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{{{42, 31, -1}, {42, 11, 31}}}
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};
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rules[8].sub = new[0];
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rules[11].sub = new[1];
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int ok = 0, pos;
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for (int msg = 0; msg < nmesg; ++msg) {
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pos = 0;
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if (match(mesg[msg], &pos, 0, 0)) {
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printf("%s: ok\n", mesg[msg]);
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ok++;
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} else {
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printf("%s: NOK\n", mesg[msg]);
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}
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}
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return ok;
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}
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static int usage(char *prg)
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{
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fprintf(stderr, "Usage: %s [-d debug_level] [-p part]\n", prg);
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return 1;
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}
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int main(ac, av)
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int ac;
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char **av;
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{
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int opt, part = 1;
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while ((opt = getopt(ac, av, "d:p:")) != -1) {
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switch (opt) {
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case 'd':
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debug_level_set(atoi(optarg));
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break;
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case 'p': /* 1 or 2 */
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part = atoi(optarg);
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if (part < 1 || part > 2)
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default:
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return usage(*av);
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}
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}
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parse();
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printf("%s : res=%ld\n", *av, part == 1? part1(): part2());
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printall();
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exit (0);
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}
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