1155-number-of-dice-rolls-with-target-sum.rb

# frozen_string_literal: true

# 1155. Number of Dice Rolls With Target Sum
# https://leetcode.com/problems/number-of-dice-rolls-with-target-sum

# @param {Integer} n
# @param {Integer} k
# @param {Integer} target
# @return {Integer}
defnum_rolls_to_target(n,k,target)
dp=Array.new(n).map{ |x| Array.new(target + 1,0)}

# fill first row
(1..target).eachdo |cell|
dp[0][cell]=1ifk >= cell
end

# fill the rest rows

(1...n).eachdo |row|
(1..target).eachdo |cell|
(1..k).eachdo |i|
dp[row][cell] += dp[row - 1][cell - i]ifcell - i >= 0
end
end
end

dp[n - 1][target] % (10**9 + 7)
end

# **************** #
# TEST #
# **************** #

require"test/unit"
classTest_num_rolls_to_target < Test::Unit::TestCase
deftest_
assert_equal1,num_rolls_to_target(1,6,3)
assert_equal6,num_rolls_to_target(2,6,7)
assert_equal222616187,num_rolls_to_target(30,30,500)
end
end