Project Euler Problem 39

問題

If p is the perimeter of a right angle triangle with integral length sides, {a,b,c},
there are exactly three solutions for p = 120.

{20,48,52}, {24,45,51}, {30,40,50}

For which value of p ≤ 1000, is the number of solutions maximised?

ソース

p (3..1000).map{|l|
	count = 0
	1.upto(l / 3){|a|
		a.upto((l - a) / 2){|b|
			c = l - a - b
			count += 1 if a * a + b * b == c * c
		}
	}
	[l, count]
}.sort{|a, b| b[1] <=> a[1]}[0][0]

解答

840

感想

a, b, cの組み合わせさえ出来ればあとは簡単！
長さと解の数を配列で返し、ソートしているのが特徴です。