[Link] https://leetcode.com/problems/3sum/
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import java.util.*;
class Solution {
public List<List<Integer>> threeSum(int[] nums) {
Arrays.sort(nums);
// for(List<Integer> e: nums) for()
List<List<Integer>> list = new LinkedList<> ();
for(int i = 0; i < nums.length - 2; i++) {
if(nums[i] > 0) break;
if(i > 0 && nums[i] == nums[i-1]) continue;
int start = i + 1, end = nums.length - 1;
int sum = (-1) * nums[i];
while(start < end) {
if(nums[start] + nums[end] > sum) end--;
else if(nums[start] + nums[end] == sum) {
list.add(Arrays.asList(nums[i], nums[start], nums[end]));
while(start < end && nums[start] == nums[start+1]) start++;
while(start < end && nums[end] == nums[end-1]) end--;
start++;
end--;
}
else start++;
}
}
return list;
}
}