Question Definition
Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note: The solution set must not contain duplicate triplets.
For example, given array S = `[-1, 0, 1, 2, -1, -4],
A solution set is:
[
[-1, 0, 1],
[-1, -1, 2]
]
Java Solution
public List<List<Integer>> threeSum(int[] nums) {
Arrays.sort(nums);
List<List<Integer>> result = new LinkedList<>();
for(int i = 0; i < nums.length - 2; i++){
if (i > 0 && nums[i] == nums[i - 1]) continue;
int left = i + 1, right = nums.length - 1;
while(left < right){
if(nums[i] + nums[left] + nums[right] == 0){
List<Integer> cur = new LinkedList<>();
cur.add(nums[i]);
cur.add(nums[left]);
cur.add(nums[right]);
result.add(cur);
while (left < right && nums[left] == nums[left + 1]) ++left;
while (left < right && nums[right] == nums[right - 1]) --right;
left++;
right--;
}else if(nums[i] + nums[left] + nums[right] < 0)
left++;
else
right--;
}
}
return result;
}
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