Given an array arr[] of length N and a number K, the task is to count the number of K-countdowns in the array.
A contiguous subarray is said to be a K-countdown if it is of length K and contains the integers K, K-1, K-2, …, 2, 1 in that order. For example, [4, 3, 2, 1] is 4-countdown and [6, 5, 4, 3, 2, 1] is a 6-countdown.
Examples:
Input: K = 2, arr[] = {3 2 1 2 2 1}
Output: 2
Explanation: Here, K=2 so the array has 2 2-Countdowns(2, 1). One countdown is from index 1 to 2 and the other is from index 4 to 5.
Input: K = 3, arr[] = {4 3 2 1 5 3 2 1}
Output: 2
Explanation: Here, K=3 so the array has 2 3-Countdowns(3, 2, 1)
Approach: The given array is traversed and every time the number K is encountered, it is checked if all the numbers K, K-1, K-2, … up to 1 are sequentially present in the array or not. If yes, the count is increased by 1. If the next number takes it out of sequence, then the next occurrence of K is looked for.
Below is the implementation of the above approach:
// C++ code for the above program. #include <bits/stdc++.h> using namespace std;
// Function to to count the // number of K-countdowns for // multiple queries int countKCountdown( int arr[],
int N,
int K)
{ // flag which stores the
// current value of value
// in the countdown
int flag = -1;
// count of K-countdowns
int count = 0;
// Loop to iterate over the
// elements of the array
for ( int i = 0; i < N; i++) {
// condition check if
// the elements
// of the array is
// equal to K
if (arr[i] == K)
flag = K;
// condition check if
// the elements
// of the array is in
// continuous order
if (arr[i] == flag)
flag--;
// condition check if
// the elements
// of the array are not
// in continuous order
else
flag = -1;
// condition check to
// increment the counter
// if the there is a
// K-countdown present
// in the array
if (flag == 0)
count++;
}
// returning the count of
// K-countdowns
return count;
} // Driver Code int main()
{ int N = 8;
int K = 3;
int arr[N] = { 4, 3, 2, 1,
5, 3, 2, 1 };
// Function Call
cout << countKCountdown(arr, N, K);
} |
// Java code for the above program. class GFG{
// Function to to count the // number of K-countdowns for // multiple queries public static int countKCountdown( int arr[],
int N, int K)
{ // Flag which stores the
// current value of value
// in the countdown
int flag = - 1 ;
// Count of K-countdowns
int count = 0 ;
// Loop to iterate over the
// elements of the array
for ( int i = 0 ; i < N; i++)
{
// Condition check if the
// elements of the array is
// equal to K
if (arr[i] == K)
flag = K;
// Condition check if the
// elements of the array is
// in continuous order
if (arr[i] == flag)
flag--;
// Condition check if the
// elements of the array are
// not in continuous order
else
flag = - 1 ;
// Condition check to increment
// the counter if the there is a
// K-countdown present in the array
if (flag == 0 )
count++;
}
// Returning the count of
// K-countdowns
return count;
} // Driver code public static void main(String[] args)
{ int N = 8 ;
int K = 3 ;
int arr[] = { 4 , 3 , 2 , 1 , 5 , 3 , 2 , 1 };
System.out.print(countKCountdown(arr, N, K));
} } // This code is contributed by divyeshrabadiya07 |
# Python3 code for the above program. # Function to to count the # number of K-countdowns for # multiple queries def countKCountdown(arr, N, K):
# flag which stores the
# current value of value
# in the countdown
flag = - 1 ;
# count of K-countdowns
count = 0 ;
# Loop to iterate over the
# elements of the array
for i in range ( 0 , N):
# condition check if
# the elements
# of the array is
# equal to K
if (arr[i] = = K):
flag = K;
# condition check if
# the elements
# of the array is in
# continuous order
if (arr[i] = = flag):
flag - = 1 ;
# condition check if
# the elements
# of the array are not
# in continuous order
else :
flag = - 1 ;
# condition check to
# increment the counter
# if the there is a
# K-countdown present
# in the array
if (flag = = 0 ):
count + = 1 ;
# returning the count of
# K-countdowns
return count;
# Driver Code N = 8 ;
K = 3 ;
arr = [ 4 , 3 , 2 , 1 ,
5 , 3 , 2 , 1 ];
# Function Call print (countKCountdown(arr, N, K))
# This code is contributed by Akanksha_Rai |
// C# code for the above program. using System;
class GFG{
// Function to to count the // number of K-countdowns for // multiple queries public static int countKCountdown( int []arr,
int N, int K)
{ // Flag which stores the
// current value of value
// in the countdown
int flag = -1;
// Count of K-countdowns
int count = 0;
// Loop to iterate over the
// elements of the array
for ( int i = 0; i < N; i++)
{
// Condition check if the
// elements of the array is
// equal to K
if (arr[i] == K)
flag = K;
// Condition check if the
// elements of the array is
// in continuous order
if (arr[i] == flag)
flag--;
// Condition check if the
// elements of the array are
// not in continuous order
else
flag = -1;
// Condition check to increment
// the counter if the there is a
// K-countdown present in the array
if (flag == 0)
count++;
}
// Returning the count of
// K-countdowns
return count;
} // Driver code public static void Main()
{ int N = 8;
int K = 3;
int []arr = { 4, 3, 2, 1, 5, 3, 2, 1 };
Console.Write(countKCountdown(arr, N, K));
} } // This code is contributed by Akanksha_Rai |
<script> //Javascript code for the above program. // Function to to count the // number of K-countdowns for // multiple queries function countKCountdown( arr, N, K)
{ // flag which stores the
// current value of value
// in the countdown
var flag = -1;
// count of K-countdowns
var count = 0;
// Loop to iterate over the
// elements of the array
for ( var i = 0; i < N; i++) {
// condition check if
// the elements
// of the array is
// equal to K
if (arr[i] == K)
flag = K;
// condition check if
// the elements
// of the array is in
// continuous order
if (arr[i] == flag)
flag--;
// condition check if
// the elements
// of the array are not
// in continuous order
else
flag = -1;
// condition check to
// increment the counter
// if the there is a
// K-countdown present
// in the array
if (flag == 0)
count++;
}
// returning the count of
// K-countdowns
return count;
} var N = 8;
var K = 3;
var arr = [ 4, 3, 2, 1, 5, 3, 2, 1 ];
// Function Call document.write( countKCountdown(arr, N, K)); // This code is contributed by SoumikMondal </script> |
2
Time Complexity: O(N)
Auxiliary Space Complexity: O(1)