Added day 17, day21, day22 solutions

Author: avidLearnerInProgress

30-days-of-code-may/17.permutationsInString.cpp

@@ -0,0 +1,42 @@
+class Solution {
+public:
+    bool checkInclusion(string s1, string s2) {
+       if(s2.size() < s1.size()) return false;
+    
+    std::vector<int> vs1(26, 0);
+    
+    for(const auto &el: s1)
+    {
+        vs1[el - 'a']++;
+    }
+
+    std::vector<int> vtmp(26, 0);
+    const std::string tmp = s2.substr(0, s1.size());
+
+    for(const auto &el: tmp)
+    {
+        vtmp[el - 'a']++;
+    }
+
+    if(vtmp == vs1)
+    {
+        return true;
+    }
+
+    for(size_t i = 1; i <= s2.size() - s1.size(); i++)
+    {   
+        const auto c1 = s2[i-1];
+        const auto c2 = s2[i+s1.size()-1];
+
+        vtmp[c1 - 'a']--;
+        vtmp[c2 - 'a']++;
+
+        if(vtmp == vs1)
+        {
+            return true;
+        }
+    }
+
+    return false;
+}
+};

…of-code-may/20.countSubmatricesWith0.cpp …of-code-may/21.countSubmatricesWith0.cpp30-days-of-code-may/20.countSubmatricesWith0.cpp renamed to 30-days-of-code-may/21.countSubmatricesWith0.cpp 30-days-of-code-may/20.countSubmatricesWith0.cpp renamed to 30-days-of-code-may/21.countSubmatricesWith0.cpp

@@ -0,0 +1,21 @@
+class Solution {
+public:
+    string frequencySort(string s) {
+        if(s.empty()) return "";
+        map<char,int> m;
+        for(auto c : s) m[c]++;
+        vector<pair<int,int>> values(m.begin(),m.end());
+        
+        sort(values.begin(),values.end(),[](const pair<int,int>& a, const pair<int,int>& b){ 
+            return a.second > b.second;
+        });
+        
+        string result = "";
+        for(auto [k, v] : values){
+            while(v--){
+                result.push_back(k);
+            }
+        }
+        return result;
+    }
+};