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47 lines
1.0 KiB
47 lines
1.0 KiB
=begin
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File: permutations_i.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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### 回溯算法：全排列 I ###
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def backtrack(state, choices, selected, res)
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# 当状态长度等于元素数量时，记录解
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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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# 遍历所有选择
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choices.each_with_index do |choice, i|
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# 剪枝：不允许重复选择元素
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unless selected[i]
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# 尝试：做出选择，更新状态
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selected[i] = true
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state << choice
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# 进行下一轮选择
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backtrack(state, choices, selected, res)
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# 回退：撤销选择，恢复到之前的状态
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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 I ###
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def permutations_i(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, 3]
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res = permutations_i(nums)
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puts "输入数组 nums = #{nums}"
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puts "所有排列 res = #{res}"
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end
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