package com.haxitable.java;

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

public class seven {
	
	//方法一：哈希法
	 public List<List<Integer>> threeSum(int[] nums) {
		 List<List<Integer>> result = new ArrayList<>();
		 Arrays.sort(nums);
		 
		 for(int i = 0; i < nums.length; i++) {
			 if(nums[i] > 0) {
				 return result;
			 }
			 
			 if(i > 0 && nums[i] == nums[i-1]) {
				 continue;
			 }
			 
			 int left = i + 1;
			 int right = nums.length - 1;
			 while(right > left) {
				 int sum = nums[i] + nums[left] + nums[right];
				 if(sum > 0) {
					 right--;
				 }else if(sum < 0) {
					 left++;
				 }else {
					 result.add(Arrays.asList(nums[i] , nums[left], nums[right]));
					 
					 //移动right和left继续循环
					 while(right > left && nums[right] == nums[right-1]) {
						 right--;
					 }
					 while(right > left && nums[left] == nums[left+1]) {
						 left++;
					 }
					 right--;
					 left++;
				 }
				 
			 }
			 
			 
		 }
		
		 return result;
	 }
}