description
Given a n array of integers and a target nums target, if there are four elements a, b, c, and d nums determined such that a + b + c + d is equal to the value of the target? Identify all satisfy the conditions of the quad and do not repeat.
Note:
The answer can not contain duplicate quad.
Examples of
ideas
Sum Noriyuki same three number
answer
- python
class Solution:
def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
res=[]
nums.sort()
n=len(nums)
for i in range(n-3):
if i-1>=0 and nums[i]==nums[i-1]: continue
if nums[i]+nums[i+1]+nums[i+3]+nums[i+2]>target: break
if nums[i]+nums[n-1]+nums[n-2]+nums[n-3]<target: continue
for j in range(i+1,n-2):
if j-1>=i+1 and nums[j]==nums[j-1]: continue
if nums[i]+nums[j]+nums[j+1]+nums[j+2]>target: break
if nums[i]+nums[j]+nums[n-1]+nums[n-2]<target: continue
a,b = j+1, len(nums)-1
while a<b:
t = nums[i]+nums[j]+nums[a]+nums[b]
if t<target: a+=1
if t>target: b-=1
if t==target:
res.append([nums[i],nums[j],nums[a],nums[b]])
while a<b and nums[b]==nums[b-1]: b-=1
while a<b and nums[a]==nums[a+1]: a+=1
a+=1
b-=1
return res
- c++
class Solution {
public:
vector<vector<int>> fourSum(vector<int>& nums, int target) {
sort(nums.begin(), nums.end());
vector<vector<int>> res;
int n=nums.size();
for (int i=0; i<n-3; i++)
{
if (i-1>=0 && nums[i]==nums[i-1]) continue;
if (nums[i]+nums[i+1]+nums[i+2]+nums[i+3]>target) break;
if (nums[i]+nums[n-1]+nums[n-2]+nums[n-3]<target) continue;
for (int j=i+1; j<n-2; j++)
{
if (j-1>=i+1 && nums[j]==nums[j-1]) continue;
if (nums[i]+nums[j]+nums[j+1]+nums[j+2]>target) break;
if (nums[i]+nums[j]+nums[n-1]+nums[n-2]<target) continue;
int a=j+1, b=nums.size()-1;
while (a<b)
{
int t = nums[i]+nums[j]+nums[a]+nums[b];
if (t<target) a++;
if (t>target) b--;
if (t==target)
{
vector<int> temp = {nums[i],nums[j],nums[a],nums[b]};
res.push_back(temp);
while (a<b && nums[b]==nums[b-1]) b--;
while (a<b && nums[a]==nums[a+1]) a++;
b--;
a++;
}
}
}
}
return res;
}
};
