Merge pull request #651 from vishvarana/main

Smallest distinct window problem using c++

Author: smv1999

Strings/smallestdistinctwindow.cpp

@@ -0,0 +1,55 @@
+//Two string given S and P, S being the main string and P being the substring or partial string.
+//We need to find the window in main string S which has all the characters of P and display it.
+//Time complexity - O(n^2)
+//Space complexity - O(1)
+
+#include<bits/stdc++.h>
+using namespace std;
+
+string smallestWindow(string s,string p){
+    unordered_map<char,int> freqp;
+    for(char c:p){
+        freqp[c]++; //taking in every character of the partial string
+    }
+    int distinct=freqp.size();
+    unordered_map<char,int> freqw;
+    int count=0;
+
+    int l=0,r=0,ans=INT_MAX,ri=-1,li=-1;
+    bool flag=false;
+
+    while(r<s.length()){
+        while(r<s.length() && count<distinct){
+            freqw[s[r]]++; //taking in the main string
+            if(freqp.find(s[r])!=freqp.end() && freqw[s[r]]==freqp[s[r]]){
+                count++; //if the char matches than count increased
+            }
+            r++; //increment uptil the main string length
+        }
+        while(l<=r && count==distinct){
+            if(ans>r-l){
+                ans=r-l;
+                li=l;
+                ri=r;
+                flag=true; //setting the flag  true if window found
+            }
+            freqw[s[l]]--;
+            if(freqp.find(s[l])!=freqp.end()&& freqw[s[l]]<freqp[s[l]]){
+                count--; 
+            }
+            l++;
+        }
+    }
+    if(!flag){
+        return "";
+    }
+    string res=s.substr(li,ri-li);
+    return res;
+}
+
+int main(){
+    string s="timetopractice";
+    string p="toc";
+    cout<<smallestWindow(s,p);
+    return 0;
+}