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Commit 0c203be

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author
hj.tian
committed
feat: add leetcode75 day35
feat: add leetcode75 day35
1 parent 5bf1117 commit 0c203be

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2 files changed

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‎leetcode75/day35_39.py

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from collections import defaultdict
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from typing import List
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class Solution:
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def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
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"""
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动态规划
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2 3 6 7
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0
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1
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2
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3
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4
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5
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6
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7
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{
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0: [[]]
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2: [[] + [2]] = [[2]]
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4: [[2] + [2]] = [[2,2]]
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6: [[2,2] + [2], [3]+[3], []+[6]] = [[2,2.2], [3,3], [6]]
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3: [[] + [3]] [[3]]
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5: [[2] + [3]]
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7: [[2,2] + [3], [0] + [7]] = [[2,2,3], [7]]
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}
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"""
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dp = defaultdict(list)
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dp[0] = [[]]
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for candidate in candidates:
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for num in range(1, target + 1):
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if num >= candidate and dp[num - candidate]:
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dp[num].extend([case + [candidate] for case in dp[num - candidate]])
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return dp[target]
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# class Solution:
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# def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
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# """
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# 搜索 + 剪枝
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# 7
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# -2 -3 -6 -7
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# -2 -3 -6 -7
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# -2 -3 -6 -7
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# -2 -3 -6 -7
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# """
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# self.ans = []
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# candidates.sort()
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# self.dfs(candidates, 0, target, [])
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# return self.ans
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# def dfs(self, candidates, index, target, path):
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# if target == 0:
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# self.ans.append(path)
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# return
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# for i in range(index, len(candidates)):
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# if target - candidates[i] < 0:
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# break
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# # self.dfs(candidates, i, target - candidates[i], path + [candidates[i]])
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# target -= candidates[i]
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# pre_path = [num for num in path]
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# path.append(candidates[i])
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# self.dfs(candidates, i, target, path)
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# target += candidates[i]
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# path = pre_path
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if __name__ == "__main__":
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assert Solution().combinationSum(candidates=[2, 3, 6, 7], target=7) == [[2, 2, 3], [7]]
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assert Solution().combinationSum(candidates=[2, 3, 5], target=8) == [[2, 2, 2, 2], [2, 3, 3], [3, 5]]
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assert Solution().combinationSum(candidates=[2], target=1) == []

‎leetcode75/day35_46.py

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from itertools import permutations
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from typing import List
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class Solution:
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def permute(self, nums: List[int]) -> List[List[int]]:
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"""4. 使用 itertools"""
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return [list(item) for item in permutations(nums)]
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# class Solution:
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# def permute(self, nums: List[int]) -> List[List[int]]:
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# """3. 搜索+
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# 1 2 3
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# 2 3
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# 3 2
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# """
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# self.ans = []
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# visit = [False for _ in nums]
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# self.dfs(nums, visit, [])
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# return self.ans
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# def dfs(self, nums, visit, item):
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# if len(item) == len(nums):
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# self.ans.append(item)
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# return
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# for i in range(len(nums)):
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# if visit[i] is False:
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# visit[i] = True
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# self.dfs(nums, visit, item + [nums[i]])
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# visit[i] = False
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# class Solution:
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# def permute(self, nums: List[int]) -> List[List[int]]:
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# """2. 迭代
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# 先解决子问题, 推导出大问题
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# dp[0] = [[1]]
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# # dp[i] 是前一项 dp[i-1] 每个 item 的每个位置插入 nums[i]
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# dp[1] = [
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# item[:index] + nums[1] + item[index:]
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# for item in dp[0]
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# for index in range(len(item) + 1)
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# ]
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# """
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# # dp = [[] for _ in nums]
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# # dp[0] = [[nums[0]]]
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# # for i in range(1, len(nums)):
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# # for sub in dp[i - 1]:
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# # for j in range(len(sub) + 1):
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# # dp[i].append(sub[:j] + [nums[i]] + sub[j:])
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# # return dp[len(nums) - 1]
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# # 空间优化, dp[i] 只与 dp[i-1]相关
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# dp_0 = [[nums[0]]]
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# for i in range(1, len(nums)):
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# dp_1 = []
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# for sub in dp_0:
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# for j in range(len(sub) + 1):
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# dp_1.append(sub[:j] + [nums[i]] + sub[j:])
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# dp_0 = dp_1
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# return dp_0
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# class Solution:
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# def permute(self, nums: List[int]) -> List[List[int]]:
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# """1. 递归
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# 要解决大问题,先解决子问题
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# 如果我解决了 permute(nums[1:]), 如何得到 premute(nums) 的答案呢?
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# for sub in permute(nums[1:]):
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# for i in range(len(sub) + 1):
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# sub[:i] + nums[0] + sub[i:]
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# 即将 nums[0] 插在每个item的每个位置
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# """
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# if len(nums) == 1:
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# return [[nums[0]]]
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# per_permute = self.permute(nums[1:])
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# ans = []
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# for sub in per_permute:
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# for i in range(len(sub) + 1):
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# ans.append(sub[:i] + [nums[0]] + sub[i:])
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# return ans
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if __name__ == "__main__":
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assert sorted(Solution().permute(nums=[1, 2, 3])) == sorted(
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[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
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)
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assert sorted(Solution().permute(nums=[0, 1])) == sorted([[0, 1], [1, 0]])
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assert Solution().permute(nums=[1]) == [[1]]

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