15. 三数之和

package leetcode;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class demo_15 {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> ll =new ArrayList<List<Integer>>();
        if(nums.length<3) {
            return ll;
        }
        //对数组进行排序
        Arrays.sort(nums);
        for(int i=0;i<nums.length-2;i++) {
            if(nums[i]>0) {break;}
            //排除重复
            if(i>0&&nums[i]==nums[i-1]) {continue;}
            int left=i+1;
            int right=nums.length-1;
            while(left<right) {
                if(left<right&&nums[left]+nums[right]+nums[i]==0) {
                    List<Integer> l=new ArrayList<Integer>();
                    l.add(nums[i]);
                    l.add(nums[left]);
                    l.add(nums[right]);
                    ll.add(l);
                    //排除重复
                    while(left<right&&nums[right]==nums[right-1]) {
                        right=right-1;
                    }
                    //排除重复
                    while(left<right&&nums[left]==nums[left+1]) {
                        left=left+1;
                    }
                    right=right-1;
                    left=left+1;
                }
                //如果三数之和大于0就调整右边界
                if(left<right&&nums[left]+nums[right]+nums[i]>0) {
                    right=right-1;
                }
                //如果三数之和小于0就调整左边界
                if(left<right&&nums[left]+nums[right]+nums[i]<0) {
                    left=left+1;
                }
            }
        }
        System.out.println(ll);
        return ll;
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        demo_15 d15=new demo_15();
        int[] nums= {-4,-2,-2,-2,0,1,2,2,2,3,3,4,4,6,6};
        d15.threeSum(nums);
    }

}