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15. 3Sum.cpp
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15. 3Sum.cpp
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//DAY 11 PROBLEM 1
//WITHOUT USING SET
class Solution {
public:
vector<vector<int>> threeSum(vector<int>& nums) {
//rest implementation is easy, just the point to keep in mind is that
//here dublicate triplets ids prohibited so we will check whether the number
//from where we begin is repeated or not .
//Because, if we start from a number, we cover all the triplets that will
//contain this number
//BUT, WE HAVE TO CHECK FOR DUBLICATES B/W J & K SEPEREATELY INSIDE THE WHILE LOOP:
vector<vector<int>>res;
if(nums.size()<3)
return res;
sort(nums.begin(),nums.end());
for(int i=0;i<nums.size();i++)
{
if(i!=0&&nums[i]==nums[i-1])
continue;
int j=i+1,k=nums.size()-1;
while(j<k)
{
//CHECKING FOR DUBLICATES B/W J& K
if(j>i+1&&j<k&&nums[j]==nums[j-1])
{
while(j<k&&nums[j]==nums[j-1])
j++;
continue;
}
if((nums[j]+nums[k])==(-nums[i]))
{
vector<int>pair;
pair.push_back(nums[i]);
pair.push_back(nums[j]);
pair.push_back(nums[k]);
res.push_back(pair);
j++;
k--;
}
else if((nums[j]+nums[k])<(-nums[i]))
{
j++;
}
else if((nums[j]+nums[k])>(-nums[i]))
{
k--;
}
}
}
//res.erase(unique(res.begin(), res.end()), res.end());
return res;
}
};