2021.01.13 연습

 

  • 사용언어 : java

 

class Solution {
    public List<Integer> findDisappearedNumbers(int[] nums) {
        
        Map<Integer, Integer> map = new HashMap<>();
        List<Integer> list = new ArrayList<Integer>();
        
        for (int i : nums) {
            map.put(i, map.getOrDefault(i, 0) + 1);
        }
        
        for (int i = 1 ; i <= nums.length; i++) {
            if (!map.containsKey(i)) {
                list.add(i);
            }
        }
        return list;
    }
}

Runtime: 22 ms, faster than 10.43% of Java online submissions for Find All Numbers Disappeared in an Array. Memory Usage: 48.8 MB, less than 13.99% of Java online submissions for Find All Numbers Disappeared in an Array.

  • 다른 코드 참고
//making numbers index negative if that number is present(Mark them visited/present)
class Solution {
    public List<Integer> findDisappearedNumbers(int[] nums) {
        
        for(int i=0;i<nums.length;i++)
        {
            int j= Math.abs(nums[i]) - 1;
            nums[j]=-1*Math.abs(nums[j]); //make negative
        }
        
        List<Integer> res = new ArrayList<>();
        
        for(int i=0;i<nums.length;i++)
        {
            if(nums[i]>0){
                res.add(i+1);
            }
        }
            return res;
    }
}