【Hot100】15. Sum of three numbers

15. Sum of three numbers
Medium question

Sum of two numbers

Sort + Double pointer
Refer to the explanation of the question ：https://leetcode.cn/problems/3sum/solution/3sumpai-xu-shuang-zhi-zhen-yi-dong-by-jyd/

class Solution {
    
    public List<List<Integer>> threeSum(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, 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(new ArrayList<Integer>(Arrays.asList(nums[k], nums[i], nums[j])));
                    while(i < j && nums[i] == nums[++i]);
                    while(i < j && nums[j] == nums[--j]);
                }
            }
        }
        return res;
    }
}