[dylan-jung] WEEK 01 solutions

contains-duplicate/dylan-jung.cpp

@@ -0,0 +1,11 @@
+class Solution {
+public:
+    bool containsDuplicate(vector<int>& nums) {
+        unordered_set<int> s;
+        for(auto item: nums) {
+            if(s.count(item) > 0) return true;
+            s.insert(item);
+        }
+        return false;
+    }
+};

house-robber/dylan-jung.cpp

@@ -0,0 +1,20 @@
+class Solution {
+public:
+    int dp[100] = { 0 };
+    int rob(vector<int>& nums) {
+        dp[0] = nums[0];
+        if(nums.size() >= 2) {
+            dp[1] = nums[1];
+        }
+        for(int i = 2; i < nums.size(); i++) {
+            for(int j = 0; j < i-1; j++) {
+                dp[i] = max(dp[j] + nums[i], dp[i]);
+            }
+        }
+        int m = -1;
+        for(int i = 0; i < nums.size(); i++) {
+            m = max(dp[i], m);
+        }
+        return m;
+    }
+};

longest-consecutive-sequence/dylan-jung.cpp

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+class Solution {
+public:
+    int longestConsecutive(vector<int>& nums) {
+        auto s = unordered_set<int>();
+        for(int it : nums) {
+            s.insert(it);
+        }
+
+        int m = 0;
+        for(int it : s) {
+            if(s.count(it-1) > 0) continue;
+
+            int cnt = 0;
+            while(s.count(it+cnt) > 0){
+                cnt++;
+            }
+            m = max(m, cnt);
+        }
+
+        return m;
+    }
+};

top-k-frequent-elements/dylan-jung.cpp

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+class Solution {
+public:
+    vector<int> topKFrequent(vector<int>& nums, int k) {
+        unordered_map<int, int> m;
+        map<int, vector<int>> freq;
+        for(auto i: nums) m[i] += 1;
+        for(auto item: m) {
+            auto [k, v] = item;
+            freq[v].push_back(k);
+        }
+
+        vector<int> ans;
+        ans.reserve(k);
+        auto it = freq.rbegin();
+        while(k > 0) {
+            auto kth = it->second;
+            ans.insert(ans.end(), kth.begin(), kth.end());
+            k-=kth.size();
+            it++;
+        }
+        return ans;
+    }
+};

two-sum/dylan-jung.cpp

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+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        vector<tuple<int, int>> arr;
+        arr.reserve(nums.size());
+        for(int i = 0; i < nums.size(); i++) {
+            arr.push_back({nums[i], i});
+        }
+        int s = 0; int e = nums.size()-1;
+        sort(arr.begin(), arr.end());
+        while(s < e) {
+            if(get<0>(arr[s]) + get<0>(arr[e]) > target) e-=1;
+            else if (get<0>(arr[s]) + get<0>(arr[e]) < target) s+=1;
+            else return {get<1>(arr[s]), get<1>(arr[e])};
+        }
+        return {};
+    }
+};