003Two Sum

def twoSum(nums: list[int], target: int) -> list[int]:
    seen = {}  # value -> index
    for i, num in enumerate(nums):
        complement = target - num
        if complement in seen:
            return [seen[complement], i]
        seen[num] = i
    return []

public int[] twoSum(int[] nums, int target) {
    Map<Integer, Integer> seen = new HashMap<>();
    for (int i = 0; i < nums.length; i++) {
        int complement = target - nums[i];
        if (seen.containsKey(complement))
            return new int[]{seen.get(complement), i};
        seen.put(nums[i], i);
    }
    return new int[]{};
}

fun twoSum(nums: IntArray, target: Int): IntArray {
    val seen = mutableMapOf<Int, Int>()
    for ((i, num) in nums.withIndex()) {
        val complement = target - num
        if (complement in seen)
            return intArrayOf(seen[complement]!!, i)
        seen[num] = i
    }
    return intArrayOf()
}

vector<int> twoSum(vector<int>& nums, int target) {
    unordered_map<int,int> seen;
    for (int i = 0; i < nums.size(); i++) {
        int complement = target - nums[i];
        if (seen.count(complement))
            return {seen[complement], i};
        seen[nums[i]] = i;
    }
    return {};
}