题解 | #三数之和#

public class Solution {
    public ArrayList<ArrayList<Integer>> threeSum(int[] num) {
        ArrayList<ArrayList<Integer>> res = new ArrayList<>();
        Arrays.sort(num);
        for(int i = 0;i < num.length ;i++){
            if(i > 0 && num[i] == num[i - 1]) continue;
            int l = i + 1;
            int r = num.length - 1;
            while(l < r){
                if(num[i] + num[l] + num[r] == 0){
                    res.add(new ArrayList<Integer>(Arrays.asList(num[i],num[l],num[r])));
                    while(l < r && num[l] == num[l + 1]) l++;
                    while(l < r && num[r] == num[r - 1]) r--;
                    l++;
                    r--;
                }else if(num[i] + num[l] + num[r] < 0){
                    l++;
                }else{
                    r--;
                }
            }
        }
        return res;
    }
}