week 1

hj/week 1/AnagramGroups.cpp

@@ -1,3 +1,19 @@
-//
-// Created by hj on 9/30/24.
-//
+class Solution {
+public:
+    vector<vector<string>> groupAnagrams(vector<string>& strs) {
+        vector<vector<string>> output;
+        unordered_map<string, vector<string>> um;
+
+        for (string &str : strs) {
+            string key = str;
+            sort(key.begin(), key.end());
+            um[key].push_back(str);
+        }
+
+        for (auto &val : um) {
+            output.push_back(val.second);
+        }
+
+        return output;
+    }
+};

hj/week 1/StringEncodeAndDecode .cpp

@@ -1,3 +1,28 @@
-//
-// Created by hj on 9/30/24.
-//
+class Solution {
+public:
+
+    string encode(vector<string>& strs) {
+        string encoded = "";
+        for (auto &str : strs) {
+            encoded += to_string(str.size()) + "#" + str;
+        }
+        return encoded;
+    }
+
+    vector<string> decode(string s) {
+        vector<string> decoded;
+        int i = 0;
+
+        while (i < s.size()) {
+            int j = s.find('#', i);
+            int len = stoi(s.substr(i, j - i));
+
+            i = j + 1;
+            decoded.push_back(s.substr(i, len));
+
+            i += len;
+        }
+
+        return decoded;
+    }
+};

hj/week 1/TopKElementsInList .cpp

@@ -1,3 +1,24 @@
-//
-// Created by hj on 9/30/24.
-//
+class Solution {
+public:
+    vector<int> topKFrequent(vector<int>& nums, int k) {
+        unordered_map<int, int> um;
+        priority_queue<pair<int, int>> pq;
+        vector<int> output;
+
+        for (auto &num : nums) {
+            um[num]++;
+        }
+
+        for (auto &pair : um) {
+            pq.push({pair.second, pair.first});
+        }
+
+        while (k > 0) {
+            output.push_back(pq.top().second);
+            pq.pop();
+            k--;
+        }
+
+        return output;
+    }
+};