Created
February 17, 2016 07:37
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# support sliding window maximum in linear time | |
srand(123) | |
n = 9 | |
k = 3 | |
m = n-1 | |
a = (0..m).to_a | |
for i in 0..m do | |
#a[i] = (rand()*10).floor() | |
a[i] = (9-i).floor() | |
end | |
a = [5, 3, 6, 7, 4, 6, 1, 2, 9] | |
puts a.to_s | |
def calc_q(a, i, k) | |
q = (i..(i+k-1)).to_a | |
max = 0 | |
for j in 0..(k-1) do | |
jj = (k-1)-j | |
#puts 'a['+(i+jj).to_s+'] to q['+jj.to_s+']' | |
max = [max, a[i+jj]].max | |
q[jj] = max | |
end | |
q | |
end | |
def print_q(q) | |
puts 'q: '+(q.map{|el| el.to_s}).join(' ') | |
end | |
q = calc_q(a, 0, k) | |
print_q(q) | |
puts 'M: '+q[0].to_s | |
nw = 0 | |
for i in 1..(n-k) do | |
puts ' '*(i*3) + a[i..(i+k-1)].to_s # window | |
if i % k == 0 | |
q = calc_q(a, i, k) | |
puts ' '*(i*3) + 'q*: '+(q.map{|el| el.to_s}).join(' ') | |
qm = q[0] | |
nw = 0 | |
m = qm | |
else | |
q.shift | |
qm = q[0] | |
puts ' '*(i*3) + 'q: '+(q.map{|el| el.to_s}).join(' ') | |
puts ' '*(i*3) + 'qm: '+qm.to_s | |
ai = a[i+k-1] | |
puts ' '*(i*3) + 'a[i+k-1]: '+ai.to_s | |
nw = [nw,ai].max | |
puts ' '*(i*3) + 'nw: '+nw.to_s | |
end | |
m = [qm,nw].max | |
puts ' '*(i*3) + 'M: '+m.to_s | |
end |
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