Grind75{: target="_blank"}
문제로{: target="_blank"}

0초로 푼 이들의 답이 궁금하다

풀이1

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class Solution {
    public int[] twoSum(int[] nums, int target) {
        if(nums == null || nums.length == 0) return null;

        for(int i = 0; i < nums.length -1; i++) {
            for(int j = i+1; j < nums.length; j++) {
                if(nums[i] + nums[j] == target){
                    int[] arr = {i, j};
                    return arr;
                }
            }
        }

        return null;
    }
}

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풀이2

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class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> numMap = new HashMap<>();
        for(int i = 0; i < nums.length; i++) {
            numMap.put(nums[i], i); // key: 값, value: 인덱스
        }

        for(int i = 0; i < nums.length; i++) {
            int complement = target - nums[i];
            if(numMap.containsKey(complement) && numMap.get(complement) != i) {
                return new int[] {i, numMap.get(complement)};
            }
        }

        return new int[] {};
    }
}

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풀이3

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class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> numMap = new HashMap<>();

        for(int i = 0; i < nums.length; i++) {
            int complement = target - nums[i];
            if(numMap.containsKey(complement)) return new int[] {numMap.get(complement), i};
            else numMap.put(nums[i], i);
        }

        return new int[]{};
    }
}

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