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49 lines
1.1 KiB
49 lines
1.1 KiB
=begin
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File: permutations_ii.rb
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Created Time: 2024-05-22
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Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
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=end
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### 回溯演算法：全排列 II ###
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def backtrack(state, choices, selected, res)
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# 當狀態長度等於元素數量時，記錄解
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if state.length == choices.length
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res << state.dup
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return
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end
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# 走訪所有選擇
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duplicated = Set.new
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choices.each_with_index do |choice, i|
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# 剪枝：不允許重複選擇元素 且 不允許重複選擇相等元素
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if !selected[i] && !duplicated.include?(choice)
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# 嘗試：做出選擇，更新狀態
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duplicated.add(choice)
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selected[i] = true
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state << choice
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# 進行下一輪選擇
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backtrack(state, choices, selected, res)
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# 回退：撤銷選擇，恢復到之前的狀態
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selected[i] = false
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state.pop
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end
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end
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end
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### 全排列 II ###
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def permutations_ii(nums)
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res = []
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backtrack([], nums, Array.new(nums.length, false), res)
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res
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end
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### Driver Code ###
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if __FILE__ == $0
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nums = [1, 2, 2]
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res = permutations_ii(nums)
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puts "輸入陣列 nums = #{nums}"
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puts "所有排列 res = #{res}"
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end
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