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main.cpp
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main.cpp
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class Solution {
public:
vector<int> mysort(vector<int>& x){ //non-descending order
vector<int> arr = x;
if(arr.size() == 1){
return arr;
}
if(arr.size() == 2){
if(arr[0]>arr[1]){
int tmp = arr[0];
arr[0] = arr[1];
arr[1] = tmp;
}
return arr;
}
int midpoint = arr.size() / 2;
vector<int> lo (arr.begin(),arr.begin() + midpoint);
vector<int> hi (arr.begin() + midpoint, arr.end());
lo = mysort(lo);
hi = mysort(hi);
vector<int> retval;
retval.reserve(lo.size()+hi.size());
int ptr1 = 0, ptr2 = 0;
while(lo.size() > ptr1 && hi.size() > ptr2){
if(lo[ptr1]<hi[ptr2]){
retval.push_back((int)lo[ptr1]);
ptr1++;
if(ptr1 >= lo.size()){
retval.insert(retval.end(), hi.begin() + ptr2, hi.end());
}//end if
}else{
retval.push_back((int)hi[ptr2]);
ptr2++;
if(ptr2 >= hi.size()){
retval.insert(retval.end(), lo.begin() + ptr1, lo.end());
}//end if
}//end if lo and hi
}//end while
return retval;
}//end mysort
vector<vector<int>> threeSum(vector<int>& nums) {
vector<vector<int>> myvec;
if(nums.size() <3) return myvec;
if(nums.size() == 3){
if(nums[0] + nums[1] + nums[2] == 0){
myvec.push_back(mysort(nums));
return myvec;
}
}
vector<int> arr = mysort(nums);
bool zero_flag = false;
for(int i = 0; i< arr.size() - 2; i++){
//if(arr[i] == arr[i+1] && arr[i] !=0 ) continue;
if(i == 0 || arr[i] > arr[i-1]){
if(zero_flag && arr[i] == 0) continue;
int start = i + 1;
int end = arr.size() - 1;
int neg = arr[i] * -1;
while (start < end){
if( arr[start] + arr[end] == neg){
vector<int> mycase;
if(arr[i] == 0 && !zero_flag){
zero_flag = true;
}
mycase.push_back(arr[i]);
mycase.push_back(arr[start]);
start ++;
mycase.push_back(arr[end]);
end -- ;
myvec.push_back(mycase);
mycase.clear();
while(start < end && arr[end] == arr[end + 1] ) end --;
while(start < end && arr[start] == arr[start - 1] ) start ++;
//end if main
}else if(arr[start] + arr[end] > neg){
end --;
}else{
start ++;
}
if(zero_flag) break;
}//end while
}//end if
}//end for i
if(myvec.size()>=2){
for( int i = 0; i < myvec.size()-1; i++){
if(myvec[i][0] == myvec[i+1][0] && myvec[i][1] == myvec[i+1][1] && myvec[i][2] == myvec[i+1][2]){
myvec.erase(myvec.begin() + i );
}
}
}
return myvec;
}
};