三数之和(Unsolved)
给定一个包含 n 个整数的数组 nums,判断 nums 中是否存在三个元素 a,b,c ,使得 a + b + c = 0 ?找出所有满足条件且不重复的三元组。
注意:答案中不可以包含重复的三元组。
示例:
给定数组 nums = [-1, 0, 1, 2, -1, -4],
满足要求的三元组集合为:
[
[-1, 0, 1],
[-1, -1, 2]
]
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| class Solution { public List<List<Integer>> threeSum(int[] nums) { if (nums == null || nums.length <= 2) { return Collections.emptyList(); } List<List<Integer>> result = new LinkedList<>();
Arrays.sort(nums); for (int i = 0; i < nums.length - 2; i++) { if (nums[i] > 0) { return result; } if (i != 0 && nums[i] == nums[i-1]) { continue; } int head = i + 1; int tail = nums.length - 1; while (head < tail) { int sum = -(nums[head] + nums[tail]); if (sum == nums[i]) { result.add(Arrays.asList(nums[i], nums[head], nums[tail])); while (head < tail && nums[head] == nums[head+1]) { head++; } while (head < tail && nums[tail] == nums[tail-1]) { tail--; } } if (sum <= nums[i]) { tail--; } else { head++; } } }
return result; } }
|
Reference
https://leetcode-cn.com/problems/3sum/solution/san-shu-zhi-he-javajian-ji-ti-jie-by-wang-zi-hao-z/