三数之和

题目

源码

public class Solution {
    /**
     * @param numbers: Give an array numbers of n integer
     * @return: Find all unique triplets in the array which gives the sum of zero.
     */
    public List<List<Integer>> threeSum(int[] numbers) {
        // write your code here
        List<List<Integer>> result = new LinkedList<>();
        if(numbers==null||numbers.length<3){
            return result;
        }
        Arrays.sort(numbers);
        for(int i=0;i<=numbers.length-3;){
            int left=0-numbers[i];
            int low=i+1;
            int high=numbers.length-1;
            while (low<high){
                int temp=numbers[low]+numbers[high];
                //System.out.printf("temp:%d,left:%d,low:%d,high:%d\n",temp,left,low,high);
                if(temp==left){
                    List<Integer> l=new LinkedList<>();
                    l.add(numbers[i]);l.add(numbers[low]);l.add(numbers[high]);
                    //System.out.printf("%d,%d,%d\n",numbers[i],numbers[low],numbers[high]);
                    result.add(l);
                    int tempIndex=low;
                    while (low<high&&numbers[tempIndex]==numbers[low]){
                        low++;
                    }
                }else if(temp>left){
                    high--;
                }else {
                    low++;
                }


            }
            int tempIndex=i;
            while (i<=numbers.length-3&&numbers[tempIndex]==numbers[i]){
                i++;
            }
        }
        return result;
    }
}