easyDSA

How do you move all zeroes to the end of an array in place?

Q: How do you move all zeroes to the end of an array in place?

**Intuition.** Keep a **write pointer** for where the next non-zero belongs. Scan the array; each time you see a non-zero, place it at the write pointer and advance it. After the pass, everything from the write pointer onward is filled with zeros. Order of non-zeros is preserved, O(1) extra space. [0,1,0,3,12] → [1,3,12,0,0] 1 <t

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def move_zeroes(nums):
    write = 0
    for x in nums:
        if x != 0:
            nums[write] = x
            write += 1
    for i in range(write, len(nums)):
        nums[i] = 0
    return nums


# --- demo ---
print(move_zeroes([0, 1, 0, 3, 12]))   # [1, 3, 12, 0, 0]

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