Problem 81

Projekt Euler w Ruby
1

In the 5 by 5 matrix below, the minimal path sum from the top left to the bottom right, by only moving to the right and down, is indicated in bold red and is equal to 2427.

131 673 234 103 18
201 96 342 965 150
630 803 746 422 111
537 699 497 121 956
805 732 524 37 331

Find the minimal path sum, in matrix.txt (right click and ‘Save Link/Target As…’), a 31K text file containing a 80 by 80 matrix, from the top left to the bottom right by only moving right and down.

[code=ruby]matrix = File.open(“matrix.txt”,“r”) do |f|
f.read.split("\n").map{|row| row.delete(" “).split(”,").map{|cell| cell.to_i}}
end

for i in 0…matrix.size-1
for j in 0…matrix.size-1
matrix[i][j] += if i == 0 && j != 0
matrix[i][j-1]
elsif j == 0 && i != 0
matrix[i-1][j]
elsif j > 0 && i > 0
matrix[i-1][j] > matrix[i][j-1] ? matrix[i][j-1] : matrix[i-1][j]
else
0
end
end
end

p matrix[-1][-1][/code]

2

Mam tak jak kolega wyżej tylko rekurencyjnie (chociaż to jest rozwiązanie mniej praktyczne) :

[code=ruby]$matrix = File.open(“matrix.txt”,“r”) do |f|
f.read.split("\n").map{|row| row.delete(" “).split(”,").map{|cell| cell.to_i}}
end

def fun(x,y)
$matrix[x][y] +
if (x==$matrix.size-1 && y<$matrix[0].size-1)
fun(x,y+1);
elsif (x<$matrix.size-1 && y==$matrix[0].size-1)
fun(x+1,y);
elsif (x<$matrix.size-1 && y<$matrix[0].size-1)
[ fun(x+1,y) , fun(x,y+1) ].min;
else
0;
end
end

fun(0,0)[/code]