Recent problem from Codechef that uses Hashing

Author: bishopmate

Hashing/chef_and_subarrays.cpp

@@ -0,0 +1,53 @@
+/*
+
+Problem Link - https://www.codechef.com/COOK129C/problems/CSUBS
+
+Problem Statement - Chef is playing a game where he has an array A of N integers, and an integer K. He looks at every subarray of length K, and writes its sum on a piece of paper. If a number appears as the sum of multiple subarrays of length K, then he only writes down that number once.
+
+Chef is lazy and doesn't like to write numbers. You, being a friend of Chef, want to modify the array such that Chef will only write one number on his paper. In one modification you can choose any index i
+and replace A[i] with any integer.
+
+You need to find the minimum number of modifications required.
+
+*/
+
+#include<bits/stdc++.h>
+#define int long long
+
+using namespace std;
+
+void solve(int n, int k, vector<int> v){
+  int ans = 0;
+  for(int i=0; i<k; i++){
+        int maximumOccurence = 0;
+        map<int, int> ma;
+        for(int j=i; j<n; j += k){
+            maximumOccurence++;
+            ma[v[j]]++;
+        }
+        int cur = maximumOccurence-1;
+        for(auto ele:ma){
+            cur = min(cur, maximumOccurence-ele.second);
+        }
+        ans += cur;
+    }
+    cout<<ans<<"\n";
+}
+
+signed main(){
+  ios::sync_with_stdio(false);cin.tie(0);
+  int t   = 1;
+  cin >> t;
+  for(int i=1; i<=t; i++){           
+    int n,k;
+    cin>>n>>k;
+    vector<int> v(n+1);
+    for(int j=1; j<=n; j++){
+      cin>>v[j];
+    }
+    solve(n,k,v);
+  }
+  return 0;
+}
+
+// Tutorial Link to understand the solution - https://discuss.codechef.com/t/csubs-editorial/90045