k-th number in the Odd-Even sequence
Given two numbers n and k, find the k-th number in the Odd-Even sequence made of n. The Odd-Even sequence contains first contains all odd numbers from 1 to n then all even numbers in set 1 to n.
Examples :
Input : n = 5, k = 3
Output : 5
In this example, the Odd-Even is
{1, 3, 5, 2, 4}.
The third number in sequence is 5.
Naive Approach :
The first approach is simply make a Odd-Even sequence and then find k-th element in it.
C++
// CPP program to find k-th // element in the Odd-Even // sequence. #include <bits/stdc++.h> using namespace std; int findK(int n, int k) { vector<long> a; // insert all the odd // numbers from 1 to n. for (int i = 1; i < n; i++) if (i % 2 == 1) a.push_back(i); // insert all the even // numbers from 1 to n. for (int i = 1; i < n; i++) if (i % 2 == 0) a.push_back(i); return (a[k - 1]); } // Driver code int main() { long n = 10, k = 3; cout << findK(n, k) << endl; return 0; } |
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Java
// Java program to find k-th // element in the Odd-Even // sequence. import java.util.*; class GFG{ static int findK(int n, int k) { ArrayList<Integer> a = new ArrayList<Integer>(n); // insert all the odd // numbers from 1 to n. for (int i = 1; i < n; i++) if (i % 2 == 1) a.add(i); // insert all the even // numbers from 1 to n. for (int i = 1; i < n; i++) if (i % 2 == 0) a.add(i); return (a.get(k - 1)); } // Driver code public static void main(String[] args) { int n = 10, k = 3; System.out.println(findK(n, k)); } } // This code is contributed by mits |
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Python3
# Python3 code to find # k-th element in the # Odd-Even sequence. def findK (n, k ): a = list() # insert all the odd # numbers from 1 to n. i = 1 while i < n: a.append(i) i = i + 2 # insert all the even # numbers from 1 to n. i = 2 while i < n: a.append(i) i = i + 2 return (a[k - 1]) # Driver code n = 10k = 3print(findK(n, k)) # This code is contributed # by "Sharad_Bhardwaj". |
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C#
// C# program to find k-th // element in the Odd-Even // sequence. using System; using System.Collections; class GFG{ static int findK(int n, int k) { ArrayList a = new ArrayList(n); // insert all the odd // numbers from 1 to n. for (int i = 1; i < n; i++) if (i % 2 == 1) a.Add(i); // insert all the even // numbers from 1 to n. for (int i = 1; i < n; i++) if (i % 2 == 0) a.Add(i); return (int)(a[k - 1]); } // Driver code static void Main() { int n = 10, k = 3; Console.WriteLine(findK(n, k)); } } // This code is contributed by mits |
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PHP
<?php // PHP program to find k-th // element in the Odd-Even // sequence. function findK($n, $k) { $a; $index = 0; // insert all the odd // numbers from 1 to n. for ($i = 1; $i < $n; $i++) if ($i % 2 == 1) $a[$index++] = $i; // insert all the even // numbers from 1 to n. for ($i = 1; $i < $n; $i++) if ($i % 2 == 0) $a[$index++] = $i; return ($a[$k - 1]); } // Driver code $n = 10; $k = 3; echo findK($n, $k); // This code is contributed by mits. ?> |
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Output :
5
The time complexity of the above approach is O(n), for an O(1) approach read the approach discussed here.
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