【LeetCode】【HOT】15. 三数之和

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• 【LeetCode】【HOT】15. 三数之和

package hot;

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

public class Solution15 {
    public static void main(String[] args) {
        int[] nums = {-1,0,1,2,-1,-4};
        Solution15 solution = new Solution15();
        System.out.println(solution.method(nums));
    }

    private List<List<Integer>> method(int[] nums){
        Arrays.sort(nums);
        List<List<Integer>> res = new ArrayList<>();
        for(int k = 0; k < nums.length - 2; k++){
            if(nums[k] > 0) break;
            if(k > 0 && nums[k] == nums[k - 1]) continue;
            int i = k + 1;
            int j = nums.length - 1;
            while(i < j){
                int sum = nums[k] + nums[i] + nums[j];
                if(sum < 0){
                    while(i < j && nums[i] == nums[++i]);
                }else if(sum > 0){
                    while(i < j && nums[j] == nums[--j]);
                }else{
                    res.add(Arrays.asList(nums[k], nums[i], nums[j]));
                    while(i < j && nums[i] == nums[++i]);
                    while(i < j && nums[j] == nums[--j]);
                }
            }
        }
        return res;
    }
}

//时间复杂度为 O(n^2)
//空间复杂度为 O(1)