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ThreeSum.java
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ThreeSum.java
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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import static java.util.Arrays.asList;
/*
* https://leetcode.com/problems/3sum/
*/
public class ThreeSum {
public List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> list = new ArrayList<>();
Arrays.sort(nums);
for (int i = 0; i < nums.length; i++) {
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
twoSum(nums, i, list);
}
return list;
}
private void twoSum(int[] nums, int index, List<List<Integer>> list) {
int twoSum = -nums[index];
int i = index + 1, j = nums.length - 1;
while (j > i) {
if (j < nums.length - 1 && nums[j] == nums[j + 1]) {
j--;
continue;
}
int sum = nums[i] + nums[j];
if (sum == twoSum && i != index && j != index) {
list.add(asList(nums[index], nums[i], nums[j]));
i++;
j--;
} else if (sum > twoSum) {
j--;
} else {
i++;
}
}
}
public static void main(String[] args) {
System.out.println(new ThreeSum().threeSum(new int[]{-1, 0, 1, 2, -1, -4}));
// [
// [-1, 0, 1],
// [-1, -1, 2]
// ]
}
}