Ruby勉強 -- 追記：C言語の場合

C言語だとダメというわけでもないような。
A*が書きづらいというだけかな。しかし配列確保してポインタ付け替えてくだけでいいからむしろC言語の方が簡単なんじゃないかな。
言語の違いは決定的なものではないように思う。Javaでは書きたくないけど。

/* http://okajima.air-nifty.com/b/2010/01/post-abc6.html */
#include <stdio.h>
#define MAX_SIZE 100
#define _(X,Y,S) (((Y)*S)+X)

void solve_map(int x, int y, int d, char map[], int cmap[], int xs) {
	if (cmap[_(x,y,xs)]>d && map[_(x,y,xs)]==' ') cmap[_(x,y,xs)]=d;
	
	if (cmap[_(x-1,y,xs)]>d+1 && map[_(x-1,y,xs)]==' ') solve_map(x-1,y,d+1,map,cmap,xs);
	if (cmap[_(x+1,y,xs)]>d+1 && map[_(x+1,y,xs)]==' ') solve_map(x+1,y,d+1,map,cmap,xs);
	if (cmap[_(x,y-1,xs)]>d+1 && map[_(x,y-1,xs)]==' ') solve_map(x,y-1,d+1,map,cmap,xs);
	if (cmap[_(x,y+1,xs)]>d+1 && map[_(x,y+1,xs)]==' ') solve_map(x,y+1,d+1,map,cmap,xs);
}

int select_route(int x, int y, char map[], int cmap[], int xs) {
	int min_d;
	
	if (map[_(x,y,xs)]==' ') map[_(x,y,xs)]='$';

	if (map[_(x-1,y,xs)]=='S') return 1;
	if (map[_(x+1,y,xs)]=='S') return 1;
	if (map[_(x,y-1,xs)]=='S') return 1;
	if (map[_(x,y+1,xs)]=='S') return 1;

    min_d=cmap[_(x,y,xs)];
	if (cmap[_(x-1,y,xs)]<min_d && map[_(x-1,y,xs)]==' ') min_d=cmap[_(x-1,y,xs)];
	if (cmap[_(x+1,y,xs)]<min_d && map[_(x+1,y,xs)]==' ') min_d=cmap[_(x+1,y,xs)];
	if (cmap[_(x,y-1,xs)]<min_d && map[_(x,y-1,xs)]==' ') min_d=cmap[_(x,y-1,xs)];
	if (cmap[_(x,y+1,xs)]<min_d && map[_(x,y+1,xs)]==' ') min_d=cmap[_(x,y+1,xs)];

	if (cmap[_(x-1,y,xs)]==min_d && map[_(x-1,y,xs)]==' ') return select_route(x-1,y,map,cmap,xs);
	if (cmap[_(x+1,y,xs)]==min_d && map[_(x+1,y,xs)]==' ') return select_route(x+1,y,map,cmap,xs);
	if (cmap[_(x,y-1,xs)]==min_d && map[_(x,y-1,xs)]==' ') return select_route(x,y-1,map,cmap,xs);
	if (cmap[_(x,y+1,xs)]==min_d && map[_(x,y+1,xs)]==' ') return select_route(x,y+1,map,cmap,xs);
	
	return 0;
}

int main(int argc, char *argv[]) {
	char map[MAX_SIZE*MAX_SIZE];
	int cmap[MAX_SIZE*MAX_SIZE];
	int xsize, ysize;
	int sx, sy;  /* start */
	int gx, gy;  /* goal */
	FILE *f;
	char c;
	int i, x, y, pos;

	/* load data */
	if ((f=fopen(argv[1],"r"))= NULL) exit(1);
	xsize = 0;
	for (i=0,pos=0; (c=fgetc(f))!=EOF; i++) {
		if (c!='\n') { 
			map[pos++]=c;
			switch (c) {
			case 'S':
				sx=(pos-1)%xsize; sy=(pos-1)/xsize;
				break;
			case 'G':
				gx=(pos-1)%xsize; gy=(pos-1)/xsize;
				break;
			} 
		} else if (xsize==0) {
			xsize=i;
		}
	}
	ysize = i/xsize;
	fclose(f);
	for (i=0; i<xsize*ysize; i++) cmap[i] = 8192;

	/* solve */
	solve_map(sx, sy, 0, map, cmap, xsize);
	if (select_route(gx, gy, map, cmap, xsize) == 1) {
		/* print data */
		for (y=0; y<ysize; y++) {
			for (x=0; x<xsize; x++) putchar(map[_(x,y,xsize)]);
			putchar('\n');
		}
	} else {
		printf("fail!\n");
		exit(1);
	}
	return 0;
}