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34 lines
752 B
34 lines
752 B
=begin
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File: climbing_stairs_dfs_mem.rb
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Created Time: 2024-05-29
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Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
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=end
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### 记忆化搜索 ###
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def dfs(i, mem)
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# 已知 dp[1] 和 dp[2] ，返回之
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return i if i == 1 || i == 2
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# 若存在记录 dp[i] ，则直接返回之
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return mem[i] if mem[i] != -1
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# dp[i] = dp[i-1] + dp[i-2]
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count = dfs(i - 1, mem) + dfs(i - 2, mem)
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# 记录 dp[i]
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mem[i] = count
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end
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### 爬楼梯：记忆化搜索 ###
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def climbing_stairs_dfs_mem(n)
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# mem[i] 记录爬到第 i 阶的方案总数，-1 代表无记录
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mem = Array.new(n + 1, -1)
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dfs(n, mem)
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end
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### Driver Code ###
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if __FILE__ == $0
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n = 9
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res = climbing_stairs_dfs_mem(n)
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puts "爬 #{n} 阶楼梯共有 #{res} 种方案"
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end
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