[oyeong011] Week 1

contains-duplicate/oyeong011.cpp

@@ -0,0 +1,14 @@
+#include<bits/stdc++.h>
+using namespace std;
+class Solution {
+public:
+    bool containsDuplicate(vector<int>& nums) {
+        unordered_map<int, int> mp;
+        for(int a : nums){
+            if(++mp[a] >= 2){
+                return true;
+            }
+        }
+        return false;
+    }
+};

house-robber/oyeong011.cpp

@@ -0,0 +1,17 @@
+class Solution {
+public:
+    int rob(vector<int>& nums) {
+        int n = nums.size();
+        if(n == 0)return 0;
+        if(n == 1)return nums[0];
+        if(n == 2)return max(nums[0], nums[1]);
+
+        vector<int> dp(n);
+        dp[0] = nums[0];
+        dp[1] = max(nums[0], nums[1]);
+        for(int i = 2; i < n; i++){
+            dp[i] = max(dp[i - 1], dp[i - 2] + nums[i]);
+        }
+        return dp[n - 1];
+    }
+};

longest-consecutive-sequence/oyeong011.cpp

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+class Solution {
+public:
+    int longestConsecutive(vector<int>& nums) {
+        const int INF = 987654321;
+        int temp = INF, ret = 0, cur = 0;
+
+        sort(nums.begin(), nums.end());
+        for(int a : nums){
+            if(a == temp)continue;
+            if(temp == INF || temp + 1 == a){
+                cur++; temp = a;
+            } else {
+                ret = max(ret, cur); 
+                cur = 1;
+                temp = a;
+            }
+        }
+        ret = max(ret, cur);
+        return ret;
+    }
+};

top-k-frequent-elements/oyeong011.cpp

@@ -0,0 +1,16 @@
+class Solution {
+public:
+    vector<int> topKFrequent(vector<int>& nums, int k) {
+        map<int, int> mp;
+        priority_queue<pair<int, int>> pq;
+        vector<int> ans;
+
+        for(auto b : nums) mp[b]++;
+
+        for(auto p : mp) pq.push({p.second, p.first});
+
+        while(k--)ans.push_back(pq.top().second), pq.pop();
+
+        return ans;
+    }
+};

valid-palindrome/oyeong011.cpp

@@ -0,0 +1,16 @@
+class Solution {
+public:
+    bool isPalindrome(string s) {
+        string clean = "";
+        for(char c : s) {
+            if(isalnum(c)) {
+                clean += tolower(c);
+            }
+        }
+
+        string reversed = clean;
+        reverse(reversed.begin(), reversed.end());
+
+        return clean == reversed;
+    }
+};