Java实现三数之和等于0 -----(笔记)

Java实现三数之和等于0 -----(笔记)

import java.util.*;

public class Test {
    
    

    public static void main(String[] args) {
    
    
        threeSum(new int[]{
    
    -1,0,1,2,-1,-4});
    }
    public static List<List<Integer>> threeSum(int[] nums) {
    
    
        List<List<Integer>> list = new ArrayList<>();
        Arrays.sort(nums);
        //-4 -1 -1 0 1 2
        for(int i=0;i<nums.length;i++){
    
    
            if(nums[i]>0){
    
    
                break;
            }
            //如果是(num[i+1] == num[i]) -1 -1 只能用一次-1了
            if(i>0 && nums[i-1] == nums[i]) continue;
            int index = nums[i];
            int j = i+1;
            int k = nums.length-1;
            while(j<k){
    
    
                //用sum记录三数之和比较好
                if(index + nums[j] + nums[k] == 0){
    
    
                    list.add(Arrays.asList(index,nums[j],nums[k]));
                    while(j<k && nums[j+1] == nums[j]){
    
    
                        j++;
                    }
                    while(j<k && nums[k-1] == nums[k]){
    
    
                        k--;
                    }
                    j++;
                    k--;
                }else if(index + nums[j] + nums[k] > 0){
    
    
                    k--;
                }else{
    
    
                    j++;
                }
            }
        }
        list.forEach(System.out::println);
        return list;
    }

}