LeetCode-Solutions-in-Cpp17

Solutions to high-frequency interview questions of LeetCode in C++17, taking into account both efficiency and comprehensibility.

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• 用哈希表保存已访问过元素的下标（题目已说明无重复元素），只需要遍历一遍，时间复杂度为 O(n)，空间复杂度为 O(n)

class Solution {
 public:
  vector<int> twoSum(vector<int>& nums, int target) {
    unordered_map<int, int> m;
    for (int i = 0; i < size(nums); ++i) {
      int t = target - nums[i];
      if (m.count(t)) {
        return {i, m[t]};
      }
      m.emplace(nums[i], i);
    }
    return {-1, -1};
  }
};