Given an array nums of n integers, are there elements a, b, c in nums 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.
Example:
Given array nums = [-1, 0, 1, 2, -1, -4],
A solution set is:
[
[-1, 0, 1],
[-1, -1, 2]
]
曾经使用Arrays.binarySearch(nums,target);但是如果数组中有重复的target的时候,返回的标号是不确定的
难点在于返回的数组列表里不能有重复的解
对于重复元素太多的情况,可以考虑在初始化时将其去掉,但是要注意把含有重复元素的解加入rst。
class Solution {
public List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> rst = new ArrayList<List<Integer>>();
if (nums == null || nums.length == 0) {
return rst;
}
Arrays.sort(nums);
for (int a = 0; a < nums.length - 2; a++) {
if (a != 0 && nums[a] == nums[a - 1]) {
continue;
}
int target = -nums[a];
int b = a + 1;
int c = nums.length - 1;
while (b < c) {
int sum = nums[b] + nums[c];
if (sum == target) {
List<Integer> list = new ArrayList<>();
list.add(nums[a]);
list.add(nums[b]);
list.add(nums[c]);
rst.add(list);
b++;
c--;
while (b < c && nums[b] == nums[b - 1]) {
b++;
}
while (b < c && nums[c] == nums[c + 1]) {
c--;
}
} else if (sum < target) {
b++;
} else {
c--;
}
}
}
return rst;
}
}