Merge pull request #827 from sriharsha200/mytech

Longest Substring with At Least K Repeating Characters

Author: Saviour1001

Strings/Longest_Substring_with_AtLeast_K_Repeating_Characters.cpp

@@ -0,0 +1,42 @@
+/* 
+Given a string s and an integer k, return the length of the longest substring of s such that the frequency of each character in this substring is greater than or equal to k.
+Example 1:
+Input: s = "aaabb", k = 3
+Output: 3
+Explanation: The longest substring is "aaa", as 'a' is repeated 3 times.
+Example 2:
+Input: s = "ababbc", k = 2
+Output: 5
+Explanation: The longest substring is "ababb", as 'a' is repeated 2 times and 'b' is repeated 3 times.
+*/
+#include<bits/stdc++.h>
+using namespace std;
+    int longestSubstring(string s, int k) {
+        unordered_map<int,int>m; // Keep Track of frequency of each character
+        for(int i=0;i<s.length();i++)
+            m[s[i]]+=1;
+        int i=0,left=s.length(),rit=0;
+        while( i < s.length() && k <= m[s[i]]){ // Sliding it till we need our first string
+            i++;
+        }
+        if(i==(s.length()))
+            return s.length();
+        if(s.length()==0)
+            return 0;
+        if(i<s.length())
+         left=longestSubstring(s.substr(0,i),k); 
+        while(i<s.length() && m[s[i]]<k) // to check if more continious characters are having count less than k   
+            i++;
+        if((s.length()-i-1)>0)
+         rit=longestSubstring(s.substr(i,s.length()),k);   
+        int ans=max(left,rit);
+        return ans;
+    }
+    int main(){
+        string s;
+        cin>>s;
+        int k;
+        cin>>k;
+        cout<<longestSubstring(s,k);
+        return 0;
+    }