【LeetCode】Two Sum

std::vector<int> twoSum(std::vector<int> &nums, int target) {
    std::unordered_map<int, int> hashMap;   // Key: nums的值, Value: 該值在nums中的index
    auto size = nums.size();

    for (int i = 0; i < size; ++i) {
        hashMap[nums[i]] = i;
    }

    for (int i = 0; i < size; ++i) {
        int complement = target - nums[i];
        if (hashMap.count(complement) <= 0) continue;
        if (hashMap[complement] == i) continue;

        return {i, hashMap[complement]};
    }

    return {};
}

std::vector<int> twoSum(std::vector<int>& nums, int target) {
    std::unordered_map<int, int> numIndexMap; // Map to store number-index pairs

    for (int i = 0; i < nums.size(); ++i) {
        int complement = target - nums[i]; // Calculate the complement needed to achieve target sum

        // Check if the complement exists in the map
        if (numIndexMap.find(complement) != numIndexMap.end()) {
            // If found, return the indices of the current number and its complement
            return {numIndexMap[complement], i};
        }

        // Add the current number and its index to the map
        numIndexMap[nums[i]] = i;
    }

    // Return an empty vector if no solution is found
    return {};
}