1주차 문제 풀이 3개 추가

- Contains Duplicate
- Two Sum
- Top K Frequent Elements

Author: hwi-middle

contains-duplicate/hwi-middle.cpp

@@ -0,0 +1,7 @@
+class Solution {
+public:
+    bool containsDuplicate(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        return nums.end() != unique(nums.begin(), nums.end());
+    }
+};

top-k-frequent-elements/hwi-middle.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+    vector<int> topKFrequent(vector<int>& nums, int k) {
+        unordered_map<int, int> m;
+        for(auto n : nums) 
+        {
+            ++m[n];
+        }
+
+        vector<pair<int, int>> v(m.begin(), m.end());
+        sort(v.begin(), v.end(), [](const auto& a, const auto& b)
+        {
+            return a.second > b.second;
+        });
+
+        vector<int> ans;
+        ans.reserve(k);
+        for (int i = 0; i < k; ++i)
+        {
+            ans.push_back(v[i].first);
+        }
+        return ans;
+    }
+};

two-sum/hwi-middle.cpp

@@ -0,0 +1,23 @@
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        vector<int> v(2);
+        unordered_map<int, int> m;
+        for (int i = 0; i < nums.size(); ++i)
+        {
+            int num = nums[i];
+            if (m.contains(target - num))
+            {
+                v[0] = m[target - num];
+                v[1] = i;
+                return v;
+            }
+
+            m[num] = i;
+        }
+
+        v[0] = -1;
+        v[1] = -1;
+        return v;
+    }
+};