In-Place Move Zeros to End of List - Amazon Top Interview Questions


Problem Statement :


Given a list of integers nums, put all the zeros to the back of the list by modifying the list in-place. The relative ordering of other elements should stay the same.

Can you do it in \mathcal{O}(1)O(1) additional space?

Constraints

0 ≤ n ≤ 100,000 where n is the length of nums

Example 1

Input
nums = [0, 1, 0, 2, 3]


Output
[1, 2, 3, 0, 0]


Explanation
Note that [1, 2, 3] appear in the same order as in the input.


Solution :



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                        Solution in C++ :

vector<int> solve(vector<int>& nums) {
    int count = 0;

    for (int i = 0; i < nums.size(); ++i) {
        if (nums[i] != 0) {
            swap(nums[i], nums[count]);
            count++;
        }
    }
                    

                        Solution in Java :

class Solution {
    public int[] solve(int[] nums) {
        int i = 0, j = 0;
        while (j < nums.length) {
            if (nums[j] == 0)
                j++;
            else
                swap(nums, i++, j++);
        }
        return nums;
    }
    public void swap(int[] a, int i, int j) {
        if (i == j)
            return;
        int temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }
}
                    

                        Solution in Python : 
                            
class Solution:
    def solve(self, nums):
        j = 0
        for i in range(len(nums)):
            if nums[i] != 0:
                if j != i:
                    nums[j], nums[i] = nums[i], nums[j]
                j += 1

        return nums
                    

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