vector< vector<int> > result;

if (num.size()<4) return result;

sort( num.begin(), num.end() );

for(int i=0; i<num.size()-3; i++) {

//skip the duplication

if (i>0 && num[i-1]==num[i]) continue;

vector<int> n(num.begin()+i+1, num.end());

vector<vector<int> > ret = threeSum(n, target-num[i]);

for(int j=0; j<ret.size(); j++){

ret[j].insert(ret[j].begin(), num[i]);

result.push_back(ret[j]);

}

}

return result;

vector< vector<int> > result;

//sort the array (if the qrray is sorted already, it won't waste any time)

sort(num.begin(), num.end());

int n = num.size();

for (int i=0; i<n-2; i++) {

//skip the duplication

if (i>0 && num[i-1]==num[i]) continue;

int a = num[i];

int low = i+1;

int high = n-1;

while ( low < high ) {

int b = num[low];

int c = num[high];

if (a+b+c == target) {

//got the soultion

vector<int> v;

v.push_back(a);

v.push_back(b);

v.push_back(c);

result.push_back(v);

// Continue search for all triplet combinations summing to zero.

//skip the duplication

while(low<n && num[low]==num[low+1]) low++;

while(high>0 && num[high]==num[high-1]) high--;

low++;

high--;

} else if (a+b+c > target) {

//skip the duplication

while(high>0 && num[high]==num[high-1]) high--;

high--;

} else{

//skip the duplication

while(low<n && num[low]==num[low+1]) low++;

low++;

}

}

}

return result;

{

for(int i=0; i<vv.size(); i++) {

cout << "[";

for(int j=0; j<vv[i].size(); j++) {

cout << " " << vv[i][j];

}

cout << "]" << endl;;

}

{

int a[] = {1,0,-1,0,-2,2};

vector<int> n(a, a+6);

int t = 0;

vector< vector<int> > v = fourSum(n, t);

printMatrix(v);

n.clear();

int b[] = {-1,-5,-5,-3,2,5,0,4};

n.insert(n.begin(), b, b+8);

t = -7;

v = fourSum(n, t);

printMatrix(v);

return 0;