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4_sum.cpp
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4_sum.cpp
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class Solution {
private:
vector<vector<int> > calSum(vector<int> num, int target){
vector<vector<int> > subsets;
vector<int> subset;
int len = num.size();
int left;
for(int i = 0; i < len; i++){
for(int j = i + 1; j < len; j++){
int start = j + 1;
int end = len - 1;
left = target - num[i] - num[j];
while(start < end){
if(num[start] + num[end] == left){
subset.clear();
subset.push_back(num[i]);
subset.push_back(num[j]);
subset.push_back(num[start]);
subset.push_back(num[end]);
subsets.push_back(subset);
start++;
end--;
while(start < end && num[start] == num[start - 1]) start++;
while(start < end && num[end] == num[end + 1]) end--;
}
else if(num[start] + num[end] > left){
end--;
}
else{
start++;
}
}
while(j < len && num[j] == num[j + 1]){
j++;
}
}
while(i < len && num[i] == num[i + 1]){
i++;
}
}
return subsets;
}
public:
vector<vector<int> > fourSum(vector<int> &num, int target) {
sort(num.begin(), num.end());
return calSum(num, target);
}
};