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Update 0018.四数之和.md
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@ -209,34 +209,38 @@ class Solution {
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Python:
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Python:
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(版本一) 双指针
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(版本一) 双指针
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```python
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```python
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def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
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class Solution:
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result = []
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def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
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nums.sort()
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nums.sort()
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for k in range(len(nums)):
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n = len(nums)
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if nums[k] > target and nums[k] >= 0:
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result = []
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for i in range(n):
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if nums[i] > target and nums[i] > 0 and target > 0:# 剪枝(可省)
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break
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break
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if k > 0 and nums[k] == nums[k-1]:
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if i > 0 and nums[i] == nums[i-1]:# 去重
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continue
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continue
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for i in range(k+1, len(nums)):
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for j in range(i+1, n):
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if nums[k] + nums[i] > target and nums[k] + nums[i] >= 0:
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if nums[i] + nums[j] > target and target > 0: #剪枝(可省)
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break
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break
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if i > k+1 and nums[i] == nums[i-1]:
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if j > i+1 and nums[j] == nums[j-1]: # 去重
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continue
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continue
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left, right = i+1, len(nums)-1
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left, right = j+1, n-1
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while right > left:
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while left < right:
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if nums[k] + nums[i] + nums[left] + nums[right] > target:
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s = nums[i] + nums[j] + nums[left] + nums[right]
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if s == target:
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result.append([nums[i], nums[j], nums[left], nums[right]])
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while left < right and nums[left] == nums[left+1]:
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left += 1
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while left < right and nums[right] == nums[right-1]:
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right -= 1
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left += 1
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right -= 1
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right -= 1
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elif nums[k] + nums[i] + nums[left] + nums[right] < target:
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elif s < target:
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left += 1
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left += 1
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else:
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else:
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result.append([nums[k], nums[i], nums[left], nums[right]])
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while right > left and nums[right] == nums[right-1]:
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right -= 1
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while right > left and nums[left] == nums[left+1]:
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left += 1
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right -= 1
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right -= 1
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left += 1
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return result
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return result
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```
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```
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(版本二) 使用字典
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(版本二) 使用字典
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