// 1. 直接遍历

vector<int> twoSum1(vector<int>& nums, int target) {

for (int i = 0; i < nums.size() - 1; ++i) {

for (int j = i + 1; j < nums.size(); ++j) {

if (nums[i] + nums[j] == target) {

return {i, j};

}

}

}

return {};

}

// 1. 使用一个哈希表

vector<int> twoSum2(vector<int>& nums, int target) {

unordered_map<int, int> table;

for (int i = 0; i < nums.size(); ++i) {

auto it = table.find(target - nums[i]);

if (it != table.end()) {

return {it->second, i};

}

table[nums[i]] = i;

}

return {};

}

cout << "Hello World" << endl;

Solution sol;

vector<int> data {1, 5, 3, 9};

const vector<int> &res = sol.twoSum2(data, 4);

for (auto i : res) {

cout << i << endl;

}