Unique Number - III Solution Added

Author: akashmodak97

Hacker Blocks/Unique Number - III.cpp

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+/* Hacker Blocks */
+/* Title - Unique Number - III */
+/* Created By - Akash Modak */
+/* Date 7/1/2020 */
+
+
+We are given an array containg n numbers. All the numbers are present thrice except for one number which is only present once. Find the unique number. Only use - bitwise operators, and no extra space.
+
+Input Format
+First line contains the number n. Second line contains n space separated number.
+
+Constraints
+N < 10^5
+
+Output Format
+Output a single line containing the unique number
+
+Sample Input
+7
+1 1 1 2 2 2 3
+Sample Output
+3
+Explanation
+3 is present only once
+
+
+#include<iostream>
+#include<numeric>
+#include<unordered_set>
+using namespace std;
+int main() {
+	int n;
+	cin>>n;
+	int a[n];
+	for(int i=0;i<n;i++)
+	cin>>a[i];
+	unordered_set<int> s(a,a+n);
+	int sum_array = accumulate(a,a+n,0);
+	int sum_set = accumulate(s.begin(),s.end(),0);
+	cout<<(3*sum_set-sum_array)/2;	//(k*sum_set-sum_array)/(k-1) where is number of similar elements
+	return 0;
+}