3Sum
问题：
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.
思路：
双指针
他人代码：
public List<List<Integer>> threeSum(int[] num) { Arrays.sort(num); List<List<Integer>> res = new LinkedList<>(); for (int i = 0; i < num.length-2; i++) { if (i == 0 || (i > 0 && num[i] != num[i-1])) { int lo = i+1, hi = num.length-1, sum = 0 - num[i]; while (lo < hi) { if (num[lo] + num[hi] == sum) { res.add(Arrays.asList(num[i], num[lo], num[hi])); while (lo < hi && num[lo] == num[lo+1]) lo++; while (lo < hi && num[hi] == num[hi-1]) hi--; lo++; hi--; } else if (num[lo] + num[hi] < sum) lo++; else hi--; } } } return res; }
学习之处：
原文：http://www.cnblogs.com/sunshisonghit/p/4335296.html
