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]
]
题意：求三个数字合为0，并且集合不重复的结果集合。
java:
class Solution {
public List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
int len=nums.length;
if(len<3)return res;
Arrays.sort(nums);
for(int i=0;i<len;i++){
if(nums[i]>0)break;
if(i>0 && nums[i]==nums[i-1])continue;
int begin=i+1,end=len-1;
while(begin<end){
int sum=nums[i]+nums[begin]+nums[end];
if(sum==0){
List<Integer> list = new ArrayList<Integer>();
list.add(nums[i]);list.add(nums[begin]);list.add(nums[end]);
res.add(list);
begin++;end--;
while(begin<end && nums[begin]==nums[begin-1])begin++;
while(begin<end && nums[end]==nums[end+1])end--;
}else if(sum>0)end--;
else begin++;
}
}
return res;
}
}
