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_0015_3Sum.java
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_0015_3Sum.java
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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Created by goto456 on 2018/11/18.
*/
public class _0015_3Sum {
public static List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> result = new ArrayList<>();
Arrays.sort(nums);
for (int i = 0; i < nums.length; i++) {
// 用于去重
if (i != 0 && nums[i] == nums[i - 1]) {
continue;
}
// 转化成Two Sum 问题
int target = -nums[i];
int left = i + 1;
int right = nums.length - 1;
while (left < right) {
int sum = nums[left] + nums[right];
if (sum == target) {
List<Integer> triplets = Arrays.asList(nums[i], nums[left], nums[right]);
result.add(triplets);
left++;
right--;
// 用于去重
while (left < right && nums[left] == nums[left - 1]) {
left++;
}
while (left < right && nums[right] == nums[right + 1]) {
right--;
}
} else if (sum < target) {
left++;
} else {
right--;
}
}
}
return result;
}
public static void main(String[] args) {
int[] nums = {-1, 0, 1, 2, -1, -4};
System.out.println(threeSum(nums));
int[] nums2 = {0, 0, 0};
System.out.println(threeSum(nums2));
}
}