Move Zeros to Left Problem Statement

Your task is to rearrange a given array ARR such that all zero elements appear at the beginning, followed by non-zero elements, while maintaining the relative order of non-zero elements.

Example:

Input:

ARR = [1, 1, 0, 2, 0]

Output:

[0, 0, 1, 1, 2]

Explanation:

The zero elements should be at the start, hence the rearranged array should be [0, 0, 1, 1, 2]. Arrays such as [0, 0, 1, 2, 1] and [0, 0, 2, 1, 1] are incorrect as they do not maintain the relative order of non-zero elements.

Follow Up:

Attempt to solve this in linear time and constant space.

Input:

The first line contains an integer 'T' for the number of test cases.
Each test case consists of an integer 'N', the number of elements in the array 'ARR', followed by 'N' space-separated integers.

Output:

For each test case, output the modified array on a new line.

Constraints:

1

Question

Move Zeros to Left Problem Statement

Your task is to rearrange a given array ARR such that all zero elements appear at the beginning, followed by non-zero elements, while maintaining the relative order of non-zero elements.

Example:

Input:

ARR = [1, 1, 0, 2, 0]

Output:

[0, 0, 1, 1, 2]

Explanation:

The zero elements should be at the start, hence the rearranged array should be [0, 0, 1, 1, 2]. Arrays such as [0, 0, 1, 2, 1] and [0, 0, 2, 1, 1] are incorrect as they do not maintain the relative order of non-zero elements.

Follow Up:

Attempt to solve this in linear time and constant space.

Input:

The first line contains an integer 'T' for the number of test cases.
Each test case consists of an integer 'N', the number of elements in the array 'ARR', followed by 'N' space-separated integers.

Output:

For each test case, output the modified array on a new line.

Constraints:

1 <= T <= 10
1 <= N <= 10⁵
-10⁹ <= ARR[i] <= 10⁹
Time limit: 1 second

Note:

Implement the function without printing output directly. The output will be managed by the system.

Accepted Answer

Rearrange an array to move all zeros to the left while maintaining the relative order of non-zero elements.

Iterate through the array and maintain two pointers, one for zeros and one for non-zeros.
Swap elements at the two pointers if the current element is non-zero.
Continue until all elements are rearranged according to the problem statement.

Accepted Answer

l=0
for r in range(len(arr1)):
    
    if arr1[r]==0 and r!=0:
        l=r-1
        
        while l!=0 or arr1[r-1]!=0 and r!=0:
            arr1[l], arr1[r]=arr1[r], arr1[l]
            print(arr1)
            l-=1
            r-=1