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4Sum.cpp
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4Sum.cpp
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#include<iostream>
#include<vector>
using namespace std;
class Solution{
public:
void vector_sort(vector<int>& nums,int l,int r){
if(l<r){
int v=nums.at(l);
int i=l,j=r;
while(i<j){
while(i<j&&nums.at(j)>=v) j--;
nums[i]=nums[j];
while(i<j&&nums.at(i)<=v) i++;
nums[j]=nums[i];
}
nums[i]=v;
vector_sort(nums,l,i);
vector_sort(nums,i+1,r);
}
}
vector<vector<int> > fourSum(vector<int>& nums,int target){
vector_sort(nums,0,nums.size()-1);
vector<vector<int> > result;
for(int l=0;l<nums.size();l++){
if(l>0&&nums.at(l)==nums.at(l-1)){
continue;
}
for(int r=nums.size()-1;r>l+2;r--){
if(r<nums.size()-1&&nums.at(r)==nums.at(r+1)){
continue;
}
int i=l+1,j=r-1;
while(i<j){
if(i>l+1&&nums.at(i)==nums.at(i-1)){
i++;
continue;
}
if(j<r-1&&nums.at(j)==nums.at(j+1)){
j--;
continue;
}
int sum=nums.at(l)+nums.at(r)+nums.at(i)+nums.at(j);
cout<<"sum: "<<sum<<endl;
if(sum>target){
j--;
}
else if(sum<target){
i++;
}
else{
vector<int> oknums;
oknums.push_back(nums.at(l));
oknums.push_back(nums.at(i));
oknums.push_back(nums.at(j));
oknums.push_back(nums.at(r));
result.push_back(oknums);
i++;
j--;
}
}
}
}
return result;
}
};
int main(){
int n;
cin>>n;
vector<int> nums;
for(int i=0;i<n;i++){
int num;
cin>>num;
nums.push_back(num);
}
int target;
cin>>target;
Solution *solution=new Solution();
vector<vector<int> > sumnums=solution->fourSum(nums,target);
for(int i=0;i<sumnums.size();i++){
for(int j=0;j<sumnums.at(i).size();j++){
cout<<sumnums.at(i).at(j)<<", ";
}
cout<<endl;
}
return 0;
}