15.三数之和.java

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

/*
 * @lc app=leetcode.cn id=15 lang=java
 *
 * [15] 三数之和
 */

// @lc code=start
class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        Arrays.sort(nums);
        for(int i = 0;i<nums.length-2;i++){
            if(i == 0 || (i>0 && nums[i] != nums[i-1])){
                int l = i+1;
                int r = nums.length-1;
                int sum = 0-nums[i];
                while(l<r){
                    if(nums[l]+nums[r] == sum){
                        result.add(Arrays.asList(nums[i],nums[l],nums[r]));
                        while(l<r && nums[l] == nums[l+1]){
                            l++;
                        }
                        while(l<r && nums[r] == nums[r-1]){
                            r--;
                        }
                        l++;
                        r--;
                    }else if(nums[l]+nums[r]<sum){
                        while(l < r &&nums[l] == nums[l+1]){
                            l++;
                        }
                        l++;
                    }else{
                        while(l < r &&nums[r] == nums[r-1]){
                            r--;
                        }
                        r--;
                    }
                }
            }
        }
        return result;
    }

}
// @lc code=end