Check if a given array is pairwise sorted or not
An array is considered pairwise sorted if each successive pair of numbers is in sorted (nondecreasing) order. In case of odd elements, last element is ignored and result is based on remaining even number of elements.
Examples:
Input : arr[] = {10, 15, 9, 9, 1, 5}; Output : Yes Pairs are (10, 15), (9, 9) and (1, 5). All these pairs are sorted in nondecreasing order. Input : arr[] = {10, 15, 8, 9, 10, 5}; Output : No The last pair (10, 5) is not sorted.
The idea is to traverse array from left to right. Compare elements pairwise, if any pair violates property, we return false. If no pair violates property, we return false.

// CPP program to check if an array is pair wise
// sorted.
#include <bits/stdc++.h>
using
namespace
std;
// Check whether the array is pairwise sorted
// or not.
bool
checkPairWiseSorted(
int
arr[],
int
n)
{
if
(n==0  n==1)
return
true
;
for
(
int
i=0; i<n; i += 2)
if
(arr[i] > arr[i+1])
return
false
;
return
true
;
}
// Driver program to test above function
int
main()
{
int
arr[] = {2, 5, 3, 7, 9, 11};
int
n =
sizeof
(arr)/
sizeof
(arr[0]);
if
(checkPairWiseSorted(arr,n))
printf
(
"Yes"
);
else
printf
(
"No"
);
return
0;
}
Output:
Yes
Time Complexity: O(n)
Space Complexity: O(1)
Disclaimer: This does not belong to TechCodeBit, its an article taken from the below
source and credits.
source and credits: http://www.geeksforgeeks.org
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