4 SUMs
ThGiven an array S of n integers, are there elements a, b, c, and d in S 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:
For example, given array S = [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]
]
Method
Use 2 node moving, and two circulation. The time consuming is N^3
class Solution(object):
def fourSum(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[List[int]]
"""
Dict = {}
res = []
nums.sort()
for i in range(len(nums)-3):
for j in range(i + 1,len(nums)-2):
p = j + 1
q = len(nums) - 1
while p != q:
s = nums[p] + nums[q] + nums[i] + nums[j]
if s == target:
if [nums[i],nums[j],nums[p],nums[q]] not in res:
res.append([nums[i],nums[j],nums[p],nums[q]])
if s > target:
q -= 1
else:
p += 1
return res
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