From ac51c297c4fca25d6b6528e4468f374534d9ba47 Mon Sep 17 00:00:00 2001
From: Rishabh <61419244+rishabh-kothari@users.noreply.github.com>
Date: Sun, 18 Oct 2020 13:46:50 +0530
Subject: [PATCH] Create Find the only duplicate element in array

In the given problem an array is given with elements in range [1,n] where n= size of the array -1.
In the array only single element is repeating two or more times.
We find that duplicate element in o(n) time and using o(1)  space by using cycle detection algorithm.
---
 Find the only duplicate element in array | 35 ++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 Find the only duplicate element in array

diff --git a/Find the only duplicate element in array b/Find the only duplicate element in array
new file mode 100644
index 0000000..7fd1f6e
--- /dev/null
+++ b/Find the only duplicate element in array	
@@ -0,0 +1,35 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define ll long long
+
+ll findDuplicateElement(ll a[],ll n)
+{
+        ll i=a[0],j=a[0];
+        do
+        {
+            i=a[i];
+            j=a[a[j]];
+        }while(i!=j);
+        
+        j=a[0];
+        while(i!=j)
+        {
+            j=a[j];
+            i=a[i];
+        }
+        return i;
+}
+
+int main()
+{
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+  ll n,i;
+  cin>>n;
+  ll a[n];
+  for(i=0;i<n;i++)cin>>a[i];
+  
+  cout<<findDuplicateElement(a,n)<<endl;
+  
+	return 0;
+}