Restoring the permutation

Codeforces/Restoring the Permutation.cpp

@@ -0,0 +1,92 @@
+/*
+    Link to the problem statement - https://codeforces.com/contest/1506/problem/E
+*/
+
+
+#include<bits/stdc++.h>
+using namespace std;
+
+#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
+#define fr(i,n) for(int i=0;i<n;i++)
+#define int long long
+
+void solve(){
+
+    int n;
+    cin>>n;
+
+    vector<int>a(n);
+    fr(i,n)
+        cin>>a[i];
+
+    vector<bool>vis(n+1, false), vis2(n+1, false);
+    vector<int>small(n),big(n);
+
+    small[0] = a[0];
+    big[0] = a[0];
+    int largeind = a[0]-1;
+    int smallind=1;
+    vis[a[0]] = true;
+    vis2[a[0]] = true;
+
+    for(int i=1;i<n;i++)
+    {
+        if(a[i] != a[i-1])
+        {
+            small[i] = a[i];
+            vis[a[i]] = true;
+
+        }
+
+        else
+        {
+            while(vis[smallind])
+                smallind++;
+
+            small[i] = smallind;
+            vis[smallind] = true;
+            smallind++;
+        }
+    }
+
+    for(int i=1;i<n;i++)
+    {
+        if(a[i] != a[i-1])
+        {           
+            big[i] = a[i];
+            vis2[a[i]] = true;
+            largeind = a[i]-1;
+        }
+
+        else
+        {
+            while(vis2[largeind])
+                largeind--;
+
+            big[i] = largeind;
+            vis2[largeind] = true;
+            largeind--;
+        }
+    }
+
+    fr(i,n)
+        cout<<small[i]<<" ";
+    cout<<'\n';
+
+    fr(i,n)
+        cout<<big[i]<<" ";
+    cout<<'\n';
+
+
+}
+
+int32_t main(){
+
+    fast();
+    int t;
+    cin>>t;
+
+    while(t--){
+        solve();
+    }
+}