cleaner Dijkstra

2024/18/i2c

+#!/bin/mksh
+set -e
+function doone {
+	print -r -- 'static const struct ipt I[] = {'
+	while IFS= read -r line; do
+		print -r -- "	{$line},"
+	done <"$1"
+	print '};'
+}
+exec >inputs.h
+print 'struct ipt {'
+print '	unsigned x;'
+print '	unsigned y;'
+print '};'
+print
+print '#ifndef PROD'
+print
+if [[ -s c2 ]]; then
+	print '#if defined(EX2)'
+	doone c2
+	for t in 3 4 5 6 7 8 9; do
+		if [[ -s c$t ]]; then
+			print "#elif defined(EX$t)"
+			doone c$t
+		fi
+	done
+	print '#else'
+	doone c
+	print '#endif'
+else
+	doone c
+fi
+print
+print '#else'
+print
+doone i
+print
+print '#endif'
+exec >/dev/null
+exit 0

2024/18/s1.c

+#include <err.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "inputs.h"
+
+#ifndef PROD
+#define W 7
+#define Z 12
+#define SX 0
+#define SY 0
+#define EX 6
+#define EY 6
+#else
+#define W 71
+#define Z 1024
+#define SX 0
+#define SY 0
+#define EX 70
+#define EY 70
+#endif
+
+struct node {
+	struct node *next;
+	struct node *neigh[4];
+	unsigned long long cost;
+	unsigned char ok:1;
+};
+
+#define INFCOST ((unsigned long long)-1)
+
+static struct node NN[W][W];
+#define N(y,x) (&(NN[y][x]))
+
+static struct node *start;
+static struct node *finish;
+
+int
+main(void)
+{
+	unsigned int x, y, d;
+	struct node *cur, *unvis, *prev;
+	unsigned long long newcost;
+
+	for (y = 0; y < W; ++y)
+		for (x = 0; x < W; ++x) {
+			cur = N(y,x);
+			cur->neigh[0] = y == 0 ? NULL : N(y-1,x);
+			cur->neigh[1] = x == W-1 ? NULL : N(y,x+1);
+			cur->neigh[2] = y == W-1 ? NULL : N(y+1,x);
+			cur->neigh[3] = x == 0 ? NULL : N(y,x-1);
+			cur->cost = INFCOST;
+			cur->ok = 1;
+		}
+
+	for (d = 0; d < Z; ++d) {
+		cur = N(I[d].y, I[d].x);
+		cur->ok = 0;
+		for (x = 0; x < 4; ++x)
+			if (cur->neigh[x])
+				cur->neigh[x]->neigh[x ^ 2U] = NULL;
+	}
+
+	if (!((start = N(SY,SX))->ok))
+		errx(1, "no start position");
+	if (!((finish = N(EY,EX))->ok))
+		errx(1, "no end position");
+
+	/* Dijkstra 1 */
+	unvis = start;
+	prev = start;
+	for (y = 0; y < W; ++y)
+		for (x = 0; x < W; ++x) {
+			cur = N(y,x);
+			if (cur->ok) {
+				prev->next = cur;
+				prev = cur;
+			}
+		}
+
+	/* Dijkstra 2 */
+	start->cost = 0;
+
+	/* Dijkstra 3 initial */
+	cur = start;
+	prev = NULL;
+
+	/* Dijkstra 4 */
+ step4:
+	for (d = 0; d < 4; ++d)
+		if (cur->neigh[d]) {
+			newcost = cur->cost + 1;
+			if (newcost < cur->neigh[d]->cost)
+				cur->neigh[d]->cost = newcost;
+		}
+
+	/* Dijkstra 5 */
+	if (prev == NULL)
+		unvis = cur->next;
+	else
+		prev->next = cur->next;
+
+	/* Dijkstra 3 */
+	if (unvis == NULL)
+		goto step6;
+	newcost = unvis->cost;
+	prev = NULL;
+	cur = unvis;
+	while (cur->next) {
+		if (cur->next->cost < newcost) {
+			newcost = cur->next->cost;
+			prev = cur;
+		}
+		cur = cur->next;
+	}
+	cur = prev ? prev->next : unvis;
+	if (newcost < INFCOST)
+		goto step4;
+
+	/* Dijkstra 6 */
+ step6:
+	if (finish->cost == INFCOST)
+		errx(1, "no solution");
+	printf("%llu\n", finish->cost);
+	return (0);
+}