Making zero array by decrementing pairs of adjacent

Namachila November 18, 2025

0 0 7 minutes read

Given a sequence of non-negative integers, say a₁, a₂, …, a_n. Only following actions can be performed on the given sequence:

Subtract 1 from a[i] and a[i+1] both.

Find if the series can be modified into all zeros using any required number of above operations.

Examples :

Input  : 1 2
Output : NO
Explanation: Only two elements, if we subtract
1 then it will convert into [0, 1].
so answer is NO. 

Input  : 0 1 1 0
Output : YES
Explanation: Here we can choose both 1 and 
subtract 1 from them then array becomes [0, 0, 0, 
0].
So answer is YES.

Input  :  1 2 3 4
Output : NO
Explanation: if we try to subtract 1 any
number of times then array will be [0, 0, 0, 1].
[1, 2, 3, 4]->[0, 1, 3, 4]->[0, 0, 2, 3]->
[0, 0, 1, 2]->[0, 0, 0, 1].

Approach 1 :

If all adjacent elements(i, i+1) in array are equal and total number of element in array is even then it’s all element can be converted to zero. For example, if array elements are like {1, 1, 2, 2, 3, 3} then its all element is convertible into zero.
Then in this case sum of every odd positioned value are always equal to the sum of even positioned value.

Implementation:

C++

// CPP program to find if it is possible
// to make all array elements 0 by decrement
// operations.
#include <bits/stdc++.h>
using namespace std;
 
bool isPossibleToZero(int a[], int n)
{
    // used for storing the sum of even 
    // and odd position element in array.
    int even = 0, odd = 0; 
     
    for (int i = 0; i < n; i++) 
    {
        // if position is odd, store sum 
        // value of odd position in odd
        if (i & 1) 
            odd += a[i];
         
        // if position is even, store sum 
        // value of even position in even
        else
            even += a[i];
    }
     
    return (odd == even);
}
 
// Driver program
int main()
{
    int arr[] = { 0, 1, 1, 0 };
    int n = sizeof(arr) / sizeof(arr[0]);
    if (isPossibleToZero(arr, n))
        cout << "YES";
    else
        cout << "NO";
}

Java

// Java program to find if
// it is possible to make 
// all array elements 0 by
// decrement operations.
import java.io.*;
 
class GFG 
{
    static boolean isPossibleToZero(int a[],    
                                    int n)
{
    // used for storing the 
    // sum of even and odd 
    // position element in array.
    int even = 0, odd = 0; 
     
    for (int i = 0; i < n; i++) 
    {
        // if position is odd, 
        // store sum value of 
        // odd position in odd
        if ((i & 1) == 0) 
            odd += a[i];
         
        // if position is even, 
        // store sum value of 
        // even position in even
        else
            even += a[i];
    }
     
    return (odd == even);
}
 
// Driver Code
public static void main(String[] args) 
{
    int arr[] = { 0, 1, 1, 0 };
    int n = arr.length;
    if (isPossibleToZero(arr, n))
        System.out.println("YES");
    else
        System.out.println("NO");
}
}
 
// This code is contributed by m_kit

Python3

# Python3 program to find if it is 
# possible to make all array elements
# 0 by decrement operations.
def isPossibleToZero(a, n):
 
    # used for storing the 
    # sum of even and odd 
    # position element in array.
    even = 0; 
    odd = 0; 
     
    for i in range(n): 
         
        # if position is odd, store sum 
        # value of odd position in odd
        if (i & 1): 
            odd += a[i];
         
        # if position is even, store sum 
        # value of even position in even
        else:
            even += a[i];
     
    return (odd == even);
 
# Driver Code
arr = [0, 1, 1, 0];
n = len(arr);
if (isPossibleToZero(arr, n)):
    print("YES");
else:
    print("NO");
 
# This code is contributed by mits

C#

// C# program to find if
// it is possible to make 
// all array elements 0 by
// decrement operations.
using System;
 
class GFG
{
static bool isPossibleToZero(int []a, 
                             int n)
{
    // used for storing the 
    // sum of even and odd 
    // position element in array.
    int even = 0, odd = 0; 
     
    for (int i = 0; i < n; i++) 
    {
        // if position is odd, 
        // store sum value of 
        // odd position in odd
        if ((i & 1) == 0) 
            odd += a[i];
         
        // if position is even, 
        // store sum value of 
        // even position in even
        else
            even += a[i];
    }
     
    return (odd == even);
}
 
// Driver Code
static public void Main ()
{
    int []arr = {0, 1, 1, 0};
    int n = arr.Length;
    if (isPossibleToZero(arr, n))
        Console.WriteLine("YES");
    else
        Console.WriteLine("NO");
}
}
 
// This code is contributed
// by m_kit

PHP

<?php
// PHP program to find if it 
// is possible to make all
// array elements 0 by 
// decrement operations.
function isPossibleToZero($a, $n)
{
    // used for storing the 
    // sum of even and odd 
    // position element in array.
    $even = 0; $odd = 0; 
     
    for ($i = 0; $i < $n; $i++) 
    {
        // if position is odd, 
        // store sum value of 
        // odd position in odd
        if ($i & 1) 
            $odd += $a[$i];
         
        // if position is even, 
        // store sum value of 
        // even position in even
        else
            $even += $a[$i];
    }
     
    return ($odd == $even);
}
 
// Driver Code
$arr = array (0, 1, 1, 0);
$n = sizeof($arr);
if (isPossibleToZero($arr, $n))
    echo "YES";
else
    echo "NO";
 
// This code is contributed by ajit
?>

Javascript

<script>
 
// Javascript program to find if
// it is possible to make 
// all array elements 0 by
// decrement operations.
function isPossibleToZero(a, n)
{
     
    // Used for storing the 
    // sum of even and odd 
    // position element in array.
    let even = 0, odd = 0; 
 
    for(let i = 0; i < n; i++) 
    {
         
        // If position is odd, 
        // store sum value of 
        // odd position in odd
        if ((i & 1) == 0) 
            odd += a[i];
 
        // If position is even, 
        // store sum value of 
        // even position in even
        else
            even += a[i];
    }
    return (odd == even);
}
 
// Driver code
let arr = [ 0, 1, 1, 0 ];
let n = arr.length;
 
if (isPossibleToZero(arr, n))
    document.write("YES");
else
    document.write("NO");
     
// This code is contributed by mukesh07
 
</script>

Output:

YES

Approach 2: If Number formed by given array element is divisible by 11 then all elements of array also can be convertible to zero.

For ex: given array {0, 1, 1, 0}, number formed by this array is 110 then it is divisible by 11. So all elements can be converted into zero.

Implementation:

C++

// CPP implementation of the 
// above approach
#include <bits/stdc++.h>
using namespace std;
 
bool isPossibleToZero(int a[], int n)
{  
    // converting array element into number
    int num = 0;
    for (int i = 0; i < n; i++)
        num = num * 10 + a[i]; 
 
    // Check if divisible by 11
    return (num % 11 == 0);
}
 
// Driver program
int main()
{
    int arr[] = { 0, 1, 1, 0 };
    int n = sizeof(arr) / sizeof(arr[0]);
    if (isPossibleToZero(arr, n))
        cout << "YES";
    else
        cout << "NO";
}

Java

// Java implementation of the above approach
import java.io.*;
 
class GFG {
     
    static boolean isPossibleToZero(int a[], int n)
    { 
        // converting array element into number
        int num = 0;
        for (int i = 0; i < n; i++)
            num = num * 10 + a[i]; 
     
        // Check if divisible by 11
        return (num % 11 == 0);
    }
     
    // Driver program
    public static void main (String[] args)
    {
 
        int arr[] = {0, 1, 1, 0};
        int n = arr.length;
        if (isPossibleToZero(arr, n))
                System.out.println( "YES");
        else
                System.out.println ("NO");
    }
}
 
// This code is contributed by @ajit

Python3

# Python3 implementation of the 
# above approach
 
def isPossibleToZero(a, n):
     
    # converting array element 
    # into number
    num = 0;
    for i in range(n):
        num = num * 10 + a[i]; 
 
    # Check if divisible by 11
    return (num % 11 == 0);
 
# Driver Code
arr = [ 0, 1, 1, 0 ];
n = len(arr);
if (isPossibleToZero(arr, n)):
    print("YES");
else:
    print("NO");
 
# This code is contributed mits

C#

// C# implementation of the above approach
using System;
 
class GFG 
{
     
static bool isPossibleToZero(int[] a, int n)
{ 
    // converting array element into number
    int num = 0;
    for (int i = 0; i < n; i++)
        num = num * 10 + a[i]; 
 
    // Check if divisible by 11
    return (num % 11 == 0);
}
 
// Driver Code
public static void Main()
{
    int[] arr = {0, 1, 1, 0};
    int n = arr.Length;
    if (isPossibleToZero(arr, n))
        Console.WriteLine("YES");
    else
        Console.WriteLine("NO");
}
}
 
// This code is contributed 
// by Akanksha Rai

PHP

<?php
// PHP implementation of 
// the above approach
 
function isPossibleToZero($a, $n)
{ 
    // converting array 
    // element into number
    $num = 0;
    for ($i = 0; $i < $n; $i++)
        $num = $num * 10 + $a[$i]; 
 
    // Check if divisible by 11
    return ($num % 11 == 0);
}
 
// Driver Code
$arr = array( 0, 1, 1, 0 );
$n = sizeof($arr);
if (isPossibleToZero($arr, $n))
    echo "YES";
else
    echo "NO";
 
// This code is contributed ajit
?>

Javascript

<script>
 
// Javascript implementation of the above approach
function isPossibleToZero(a, n)
{ 
     
    // Converting array element into number
    let num = 0;
    for(let i = 0; i < n; i++)
        num = num * 10 + a[i]; 
 
    // Check if divisible by 11
    return (num % 11 == 0);
}
 
// Driver code
let arr = [ 0, 1, 1, 0 ];
let n = arr.length;
 
if (isPossibleToZero(arr, n))
    document.write("YES");
else
    document.write("NO");
     
// This code is contributed by divyeshrabadiya07
 
</script>

Output:

YES

The above implementation causes overflow for slightly bigger arrays. We can use below method to avoid overflow.Check if a large number is divisible by 11 or not

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