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; i++){
if(i > 0 && nums[i] == nums[i - 1])
continue;
int start = i + 1;
int end = nums.length - 1;
while(start < end){
if(nums[start] + nums[end] + nums[i] == 0){
List<Integer> temp = new LinkedList<>();
temp.add(nums[start]);
temp.add(nums[end]);
temp.add(nums[i]);
result.add(temp);
start++;
end--;
while(start < nums.length && nums[start] == nums[start - 1])
start++;
while(end >= 0 && nums[end] == nums[end + 1])
end--;
}else if(nums[start] + nums[end] + nums[i] > 0){
end--;
}else
start++;
}
}
return result;
}
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