perl

$top = 3;
$left = 3;
$top--;
$left--;
foreach(0..$top){
	$arr[0][$_] = 1;
	$arr[1][$_] = $_ + 1;
}
foreach(0..$left){
	$arr[$_][0] = 1;
	$arr[$_][1] = $_ + 1;
}

foreach $a (0..$left){
foreach $b (0..$top){
if(!defined $arr[$a][$b]){
	$arr[$a][$b] = $arr[$a-1][$b] + $arr[$a][$b-1];
}
}
}

print $arr[$top][$left];

点と線
http://www32.ocn.ne.jp/~graph_puzzle/
電磁理論
http://www-ise2.ist.osaka-u.ac.jp/~iwanaga/study/em/index.html