added C++ solution to 285C Codeforces

Codeforces/285C.cpp

@@ -0,0 +1,40 @@
+/* 
+*Problem Name (C. Building Permutation)
+
+*Problem Statement :-
+You have a sequence of integers a1, a2, ..., an. In one move, you are allowed to decrease or increase any number by one. 
+Count the minimum number of moves, needed to build a permutation from this sequence.
+
+*/
+
+#include <bits/stdc++.h>
+using namespace std;
+typedef long long ll;
+
+int main(){
+
+        ll n;cin>>n; // ll is long long data type as defined above
+        ll arr[n];
+        for(ll i=0; i<n; i++){
+            cin>>arr[i];
+        }
+
+        sort(arr,arr+n); //first we sort the array
+        ll diff =0, sum =0;
+
+        for(ll i=0; i<n; i++){
+
+            if(arr[i] != i+1){ //now we check if the current element has value equal to (i+1) If no we proceed further
+
+                diff = abs(arr[i] - (i+1)); // Now we check the absolute difference between the current element value
+                                            // and (i+1) ... (i+1) denotes that there should have been (i+1) instead of arr[i].
+
+                sum += diff;               // And we add the difference in a variable sum
+            }
+        }
+
+        cout<<sum<<"\n";
+
+
+     return 0;
+}