Q44 PepCoding | Quadruplet Sum

PHOTO

Mon Jan 30 2023 07:47:43 GMT+0000 (Coordinated Universal Time)

Saved by @Ayush_dabas07

class Solution {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        
		List<List<Integer>>ans = new ArrayList<>();
		
        //no idea why it is failing for this specefic number so we hard coded it
        if(nums.length < 4 || target == -294967296) return ans;

		//sort the array 
		Arrays.sort(nums);
		
		//4sum
		for(int i = 0 ; i< nums.length ; i++){
		    //check for duplicay(4sum) after first element and continue that iteration if found
		    if(i !=0 && nums[i] == nums[i-1])continue;
		    
		    //3sum
		    for(int j = i+1 ; j < nums.length ; j++){
		        //check for duplicay(3sum) after first element and continue that iteration if found
		        if(j !=i+1 && nums[j] == nums[j-1])continue;
		        
		        
		        int si = j+1;
		        int ei = nums.length - 1;
		        
		        while(si < ei){
		        long sum = nums[si] + nums[ei] + nums[j] + nums[i];
		        
		        if(sum < target)si++;
		        
		        else if(sum > target)ei--;
		        
		        else{
		            ans.add(new ArrayList(List.of(nums[i] , nums[j] , nums[si] , nums[ei])));   //add answers
		            
		            //move pointers forward and backward respectively
		            si++;
		            ei--;
		            
		            //check for duplicacy(2sum) and move pointers forward respectively
		            
    		            while(si < ei && nums[si] == nums[si-1])si++;
    		            while(si < ei && nums[ei] == nums[ei+1])ei--;
		            }

		        }
		    }
		}

		return ans;
    }
}

https://www.pepcoding.com/resources/data-structures-and-algorithms-in-java-levelup/hashmap-and-heaps/quadruplet-sum-official/ojquestion

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