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18. 4Sum.py
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18. 4Sum.py
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'''
Given an array nums of n integers and an integer target, are there elements a, b, c,
and d in nums such that a + b + c + d = target? Find all unique quadruplets in the
array which gives the sum of target.
Note:
The solution set must not contain duplicate quadruplets.
Example:
Given array nums = [1, 0, -1, 0, -2, 2], and target = 0.
A solution set is:
[
[-1, 0, 0, 1],
[-2, -1, 1, 2],
[-2, 0, 0, 2]
]
'''
class Solution:
def fourSum(self, nums, target):
l=len(nums)
res = []
nums.sort()
for i in range(l-3):
if i>0 and nums[i]==nums[i-1]:
continue
for j in range(i+1,l-2):
if j>i+1 and nums[j]==nums[j-1]:
continue
f = j+1
b = l-1
while(f<b):
summ = nums[i]+nums[j]+nums[f]+nums[b]
if summ>target:
b -= 1
elif summ<target:
f += 1
else:
res.append([nums[i],nums[j],nums[f],nums[b]])
while f<b and nums[f]==nums[f+1]:
f += 1
while f<b and nums[b]==nums[b-1]:
b -= 1
f += 1
b -+ 1
return res