Given an array S of n integers, are there elements abc 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] ]

 

class Solution {
   public List<List<Integer>> threeSum(int[] nums) {
      Arrays.sort(nums);
      List<List<Integer>> res = new LinkedList<>();
       for (int i = 0; i < nums.length – 2; i++) {
          if (i == 0 || (i > 0 && nums[i] != nums[i – 1])) {
             int lo = i + 1; 
             int hi = nums.length – 1;
             int sum = 0 – nums[i];
             while (lo < hi) {
                 if (nums[lo] + nums[hi] == sum) {
                   res.add(Arrays.asList(nums[i], nums[lo], nums[hi]));
                    while (lo < hi && nums[lo] == nums[lo + 1]) //略过重复的元素
                       lo++;
                    while (lo < hi && nums[hi] == nums[hi – 1])
                       hi–;
                    lo++;
                    hi–;
                 } else if (nums[lo] + nums[hi] < sum) {
                    while (lo < hi && nums[lo] == nums[lo + 1])
                       lo++;
                    lo++;
                 } else {
                    while (lo < hi && nums[hi] == nums[hi – 1])
                       hi–;
                    hi–;
                }
             }
          }
      }
       return res;
   }
}

原文地址:http://www.cnblogs.com/MarkLeeBYR/p/16850601.html

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